Electrical 
Fire  Hazards 


The  Insurance  Institute 
of  Hartford,  Inc. 

1918 


PRACTICAL  INSTRUCTION 


ON 


"Electrical  Fire  Hazards" 


By 

THOMAS   HENRY    DAY 

of  the 

New  England  Insurance  Exchange 
Boston,  Mass. 


Given  before 

THE  INSURANCE  INSTITUTE  OF  HARTFORD,  INC. 
Season  of  1917-18 


T- 


COPYRIGHT,  1918 

The  Insurance  Institute  of  Hartford,  Inc. 
Hartford,  Conn. 


Electrical  Fire  Hazards 

Part  No.  i. 

INTRODUCTION. 

Electricity  in  motion,  lights  lamps,  drives  motors,  refines 
metals,  raises  to  a  high  temperature  all  sorts  of  electrical 
heating  devices,  energizes  the  telephone,  telegraph  and  electric 
bell.  From  one  outlet  we  may  supply  an  incandescent  lamp, 
a  flat-iron,  a  coffee  percolator,  a  toaster,  an  electric  fan,  a 
heating  radiator,  a  sewing  machine  motor,  a  broiler,  a  hot- 
water  heater  and  a  number  of  other  devices.  Thus,  we  may 
from  one  simple  fixture  use  electricity  in  motion  for  light, 
heat  or  power.  Electricity  at  rest,  has  few  effects  of  practi- 
cal value.  So  we  are  to  study  electricity  only  as  it  moves, 
that  is,  flows  and  does  work. 

WHAT  IS  ELECTRICITY? 

Electricity  has  been  described  as  juice.  Since  Benjamin 
Franklin  brought  it  from  the  sky  with  a  kite,  no  better,  or 
more  scientific  definition  has  been  made.  In  a  word,  we 
cannot  tell  you  what  electricity  is.  Our  interests,  as  Fire 
Prevention  Engineers,  are  concerned  only  in  the  event  of  im- 
perfect installations  and  the  use  of  improper  devices  and  ma- 
terials which  would  constitute  a  fire  hazard  and  the  National 
Electrical  Code,  the  recognized  standard  of  electrical  installa- 
tions in  this  country  and  in  Canada,  is  confined  to  such  ques- 
tions as  wrill  provide  proper  methods  and  materials  that  such 
hazard  may  be  minimized.  We  might  say  that  the  National 
Electrical  Code  was  for  the  purpose  of  using  electricity  in  the 
capacity  of  a  servant.  Used  as  such,  it  is  safe.  When,  how- 
ever, it  is  permitted  to  become  a  master,  it  not  alone  becomes 
a  hazard,  but  a  menace,  as  well. 

ISTORY. 

Electricity  is  not  an  invention.  Like  steam,  it  is  a  dis- 
covery. Its  discovery  was  not  much,  when  viewed  in  the 
light  of  the  world  at  its  birth,  some  600  B.  C. ;  merely  a  piece 


of  amber  rubbed  against  the  clothing  of  the  Greek  Thales; 
merely  the  gaining  of  a  strange  property  of  first  attracting 
and  then  repelling  light  objects  brought  near  it.  Dr.  Gilbert, 
a  physician  to  Queen  Elizabeth,  may  be  considered  as  the 
founder  of  the  science,  as  he  appears  to  have  been  the  first 
philosopher  who  repeated  the  observations  of  the  ancients. 
The  experiments  of  Sir  Isaac  Newton,  before  the  Royal 
Society,  in  1676,  excited  surprise  and  comment.  Sir  William 
Watson  succeeded  in  firing  gunpowder  by  the  electric  spark 
and  established  the  theory  of  positive  and  negative  electricity. 

A  high  place  in  the  history  of  electricity  must  be  allotted 
to  the  name  of  Benjamin  Franklin.  His  researches  did  much 
to  extend  our  theoretical  and  practical  knowledge  of  elec- 
tricity. In  1827,  Dr.  G.  S.  Ohm  rendered  a  great  service  to 
the  science  of  electricity  by  publishing  his  mathematical 
theory  of  the  galvanic  current.  In  1831,  Faraday  began  with 
the  discovery  of  the  induction  of  electric  currents,  that 
brilliant  series  of  experimental  researches  which  has  rendered 
his  name  immortal. 

To  attempt  to  trace  the  history  of  the  dynamo-electric 
machine  would  more  than  fully  occupy  the  time  generally 
assigned  to  a  single  lecture.  Suffice  it  to  say,  that  the  first 
machine  of  this  type  was  invented  by  Faraday,  who  modestly 
described  it  merely  as  "A  New  Electrical  Machine." 

Later  came  the  successful  solution  of  the  divisibility  of 
the  electric  light  by  the  invention  of  the  incandescent  lamp. 

The  invention  of  the  dynamo  rendered  the  extended  com- 
mercial application  possible  of  another  invention,  the  electric 
motor,  which  has  been  successfully  developed  and  placed  into 
actual  use  to  an  extent  that  appears  almost  incredible.  It  has 
been  recently  stated  by  the  Society  of  Electrical  Development, 
that  electricity  is  being  used  in  over  5,000  different  ways. 

PURPOSE  OF 
ELECTRICAL  INSPECTION. 

A  fire  prevention  engineer,  or  an  electrical  inspector, 
should  not  endeavor  to  ascertain  if  the  installation  will  meet 
the  demands  of  its  intended  uses.  The  function  of  inspection 
is  single,  not  manifold.  The  one  purpose  should  be  to  examine 
the  installation,  whether  it  be  for  electric  light,  heat  or  power, 
that  weak  points,  if  any,  which  might  cause  a  fire  or  be  dan- 
gerous to  life,  may  be  pointed  out  and  corrected.  I  do  not 


think  it  would  be  wise  for  the  fire  prevention  engineer,  or 
electrical  inspector,  to  engage  in  the  engineering  problems  of 
the  installation  he  may  inspect,  but  he  should  be  capable  of 
passing  on  plans  and  the  execution  of  the  work  that  life  and 
property  may  be  safely  guarded. 

The  wisdom  in  refraining  from  engaging  in  the  electrical 
engineering  problems  of  the  installation,  may  be  seen  in  the 
several  methods  for  determining  the  size  of  conductors  to  be 
used  for  alternating  current  motors,  there  being  different  con- 
siderations for  the  varying  types  of  motors,  the  uses,  the 
power  factor,  the  voltage  and  the  starting  and  running  loads 
of  the  motors  being  different  in  the  several  types  and  locali- 
ties. The  method,  protection  and  execution  of  the  installation 
is  what  should  concern  the  fire  prevention  engineer,  or  electri- 
cal inspector. 

IRES  CAUSED  BY 
LECTRICITY. 

Among  the  problems,  subsidiary  to  the  question  of  in- 
stallation, is  the  relation  of  electricity  to  the  fire  hazard.  Vir- 
tually all  the  precautions  for  the  maintenance  of  conditions  of 
safety  may  be  found  in  the  provisions  for  adequate  conductiv- 
ity and  efficient  insulation,  as  fires  by  electricity  are  only 
caused  by  one  or  both  of  two  general  ways. 

OVERHEATING. 

FIRST: — By  the  overheating  of  conductors,  wires, 
switches  and  other  devices  which  may  result  in  a  fire  to  sur- 
rounding inflammable  material  and  objects.  Overheated 
wires  will  ignite  the  insulation  and  the  flame  will  travel  along 
the  conductor,  igniting  other  inflammable  objects  in  its  path. 
That  this  overheating  may  be  avoided,  we  should  examine 
very  closely  the  types  and  sizes  of  fuses  used.  The  old 
fashioned  link  fuses  should  never  be  permitted  unless  en- 
closed in  cabinets  of  proper  construction,  except  on  switch- 
boards located  in  rooms  of  fire  resisting  construction.  The 
so-called  fuse  wire  should  not  be  permitted,  under  any  cir- 
cumstances, because  of  the  absence  of  the  copper  terminals. 
Fuses  of  any  type  should  never  be  installed  in  locations  where 
there  are  flyings  of  ignitable  material,  dust  or  gases,  as,  even 
with  enclosed  fuses,  the  gases  formed  by  the  fusing  metal, 
in  the  fuse,  do  tear  apart  the  fuse  casing  and  the  arc,  also  the 


Courtesy   of   Commissioner  James   E.   Cole,   Wire   Dept.,   Boston,   Mass. 

Group  of  cut-outs,  parts  of  fixtures  and  sockets  burned  out.  These 
cut-outs  were  for  the  old  fashioned  link  fuses  and  had  mica  covers  which 
made  them  extremely  hazardous,  because  when  the  link  fuses  operated 
the  mica  cover  was  broken  and  thus  permitted  the  molten  fuse  metal  to 
be  expelled  from  the  cut-out.  The  use  of  this  type  of  cut-out  has  not 
been  permitted  for  a  number  of  years. 


molten  metal  will  ignite  combustible  material  and  cause  fire. 

All  conductors  are  heated  by  any  current  however  small, 
but  if  the  conductor  is  overloaded,  and  over-fused,  it  may  be- 
come hot  enough  to  ignite  the  insulation.  Hence  it  is  import- 
ant that  wires  should  be  of  sufficient  capacity  to  carry  the 
load,  and  all  conducting  parts  of  electrical  appliances  must  be 
properly  proportioned.  Overheating  of  conductors  and  de- 
vices is  thus  one  of  the  ways  in  which  electricity  may  cause 
a  fire. 

Assuming,  for  purposes  of  illustration,  that  the  con- 
ductors of  a  circuit  were  properly  proportioned  and  were 
properly  protected  by  fuses  when  they  were  installed.  With- 
out consideration  of  possibilities  the  number  of  lamps  is  in- 
creased or  a  larger  motor  replaces  the  original  motor.  When 
this  increased  load  is  thrown  upon  the  conductors,  the  fuses 
"blow"  and  open  the  circuit,  just  what  they  were  designed  to 
do.  Someone  increases  the  size  of  the  fuse,  or  worse  yet, 
substitutes  a  copper  wire,  a  hair  pin,  strips  of  iron,  brass  or 
lead,  and  I  have  even  found  ten  cent  pieces  in  the  cut-outs. 
The  lights  burn  brightly,  or  the  motor  runs  satisfactorily. 
Later,  however,  the  wires  overheat  and  the  insulation  is  ig- 
nited, thus  setting  fire  to  the  surrounding  objects. 

It  is  important  that  we  become  familiar  with  the  safe 
fusing  of  wires,  as  the  capacity  of  standard  fuses  are  plainly 
marked  on  the  outside.  The  smallest  wire  permitted  in  any 
circuit,  and  the  one  most  generally  used  on  lighting  circuits, 
is  No.  14,  B.  &  S.  gage  and  this  size  wire  should  never  bo 
fused  with  a  fuse  larger  than  15  amperes,  for  a  motor  circuit, 
nor  with  a  fuse  larger  than  10  amperes,  for  a  lighting  circuit. 

As  another  example  which  may  cause  the  wires  to  heat, 
is  that  of  a  poor  joint  or  splice  in  a  wire.  When  a  small 
amount  of  current  flows  the  heat  is  not  appreciable,  but  as  the 
current  increases,  owing  to  the  poor  contact,  the  joint  heats 
and  the  insulation  is  ignited.  All  splices  should  be  well  made 
and  should  be  mechanically  and  electricallv  secure  before 
soldering,  that  the  opportunity  for  heating  at  the  splice,  will 
be  removed.  Again,  we  may  have  this  overheating  by  poor 
connections.  A  binding  screw  is  set  up  securely,  but,  owing 
to  the  vibration  of  the  building  this  contact  becomes  loose, 
heating  takes  place  and  the  insulation  on  the  wire  is  ignited 
because  of  the  heating  conductor. 

A  few  examples  of  the  foregoing,  the  result  of  actual  field 
experience,  may  be  of  service  at  this  time. 


One  fire  was  due  to  lights  being  added  to  old  wiring  until 
some  of  the  branch  circuits  were  overloaded.  This  over- 
load and  poor  workmanship  resulted  in  a  fire  causing  a  loss 
of  $190.00. 

A  short-circuit  occurred  in  a  flexible  cord  pendant  de- 
stroying the  cord  and  burning  itself  out  at  the  ceiling 
rosette.  An  investigation  developed  the  fact  that  blown 
fuses  on  the  circuit  were  bridged  with  pennies. 

Heating  at  a  loose  contact  on  a  resistance  used  in  start- 
ing a  100  horsepower  motor,  and  rubber-covered  wire  in  close 
proximity  to  the  contact,  offered  conditions  which  started  a 
fire  in  a  packing  plant  with  a  resultant  loss  of  $200.00. 

An  amateur  extension  of  wiring  from  a  standard  equip- 
ment resulted  in  a  short-circuit  on  an  overfused  circuit  and 
a  loss  of  $7,500.00. 

A  fire  originated  from  a  short-circuit  above  a  metal 
ceiling  and  spread  through  the  open  partition  into  the  attic 
above.  The  original  electrical  installation  was  good,  but 
trouble  was  caused  by  overloading  the  circuits.  The  wiring, 
as  originally  installed,  was  for  i6-candle  power  lamps  only, 
but  these  were  afterwards  replaced  by  i5O-candle  power 
lamps  without  increasing  the  size  of  the  wrire  in  the  circuits. 
The  branch  circuits,  which  under  the  Rules  should  not  be 
fused  above  10  amperes,  were  fused  for  thirty  amperes  and 
the  main  fuse  block  was  bridged  with  strips  of  lead.  Naturally 
the  fuses  failed  to  operate  and  the  fire  caused  damage  to  the 
extent  of  $8,000.00. 

BY  THE  FORMATION 
OF  AN  ARC. 

SECOND : — Fires  are  caused  by  the  forming  of  an  "arc". 
An  arc  is  always  accompanied  by  heat,  and  if  it  is  of  sufficient 
capacity  may  not  only  ignite  combustible  material,  but  may 
melt  metals,  also.  Arcs  may  be  formed  between  the  two 
wires  of  a  circuit  when  the  wrires  are  too  close  to  each  other. 
An  arc  may  also  be  formed  between  one  wire  of  a  circuit  and 
any  grounded  metal,  or,  between  an  ungrounded  metal  and 
another  grounded  metal,  the  former  being  in  contact  with  a 
wire  of  a  circuit.  A  wooden  truss  may  be  reinforced  with  a 
long  metal  rod,  which  rod  may  be  in  contact  with  one  wire 
of  a  circuit  and  a  grounded  gas  pipe,  where,  if  a  sufficient 
amount  of  current  was  flowing,  an  arc  would  be  established,  a 
hole  melted  in  the  pipe  and  the  escaping  gas  ignited  by  the 
arc.  Perhaps  a  short-cut  definition  of  the  word  "Arc"  may 
assist  in  remembering  what  I  have  said:  "An  arc  is  the 
physical  evidence  that  current  is  flowing."  Permit  me  to 


again  draw  from  field  experience  by  way  of  illustrating  how 
fires  may  be  started  by  an  "Arc". 

As  an  example  of  an  arc  between  wires,  I  might  cite 
wrhat  may  happen  behind  the  canopy  of  a  fixture  where  the 
wires  of  the  fixture  are  joined  to  the  circuit  wires.  The 
wireman,  through  carelessness  may  fail  to  properly  tape  or 
cover  the  joints,  and  as  some  canopies  have  very  little  space 
in  the  rear  when  the  canopy  is  pushed  back,  the  wires  come 
in  contact.  When  the  current  is  turned  on,  an  arc  is  estab- 
lished between  the  conductors  which,  before  the  fuses  may 
open  may  set  fire  to  the  insulation  and  thus  to  the  building. 

As  an  example  of  an  arc  between  one  circuit  wire  and 
grounded  metal,  I  might  state  an  experience  where  one  of 
the  circuit  wires  became  grounded  on  the  gas  pipe  at  the 
fixture  outlet,  thus  establishing  an  arc,  setting  fire  to  shavings 
which  accumulated  when  the  house  was  built.  The  loss  was 
$25.00 

A  short-circuit  due  to  defective  insulation  in  a  combina- 
tion fixture  created  an  arc  of  sufficient  intensity  to  puncture 
the  gas  pipe  below  the  joint  and  ignite  the  gas,  with  a  fire 
loss  of  $50.00. 

A  metal  ceiling  was  put  in  place  over  porcelain  cleat 
work  in  a  basement  kitchen  without  the  knowledge  of  the 
inspection  department  having  jurisdiction.  The  insulation 
of  the  wire  broke  down  because  of  dampness  and  became 
grounded  on  the  metal  ceiling.  The  arcing  ignited  the  in- 
sulation on  the  wire  and  the  fire  was  communicated  to  wood- 
work, doing  considerable  damage. 

As  a  somewhat  different  example  of  an  arc  the  following 
is  most  interesting. 

The  property  consisted  of  a  group  of  buildings,  some  of 
which  were  used  as  stores,  some  for  light  manufacturing,  the 
principal  occupancy  being  a  hotel.  On  the  front  of  the  hotel 
is  a  fire  escape  which  acted  as  an  electric  conductor.  Among 
the  wires  in  front  of  the  building  are  some  street  railway  feed- 
ers. These  feeders  were  erected  before  the  fire  escape  was 
placed  on  the  building  and  with  the  putting  in  place  of  the 
escape,  the  feeders  were  encased  in  wooden  sleeves  where  too 
close  to  the  iron  work.  During  a  noon  hour  one  of  these 
250,000  circular  mill  feeders,  unprotected  because  of  damage 
to  the  wooden  sleeve,  came  in  contact  with  a  handrail  support, 
and  an  arc  was  formed  which  lasted  until  the  cable  fused  and 
fell  apart,  also  fusing  the  handrail.  The  fire  escape  extends 
from  the  first  to  the  fifth  floors  with  a  platform  at  each  floor. 
Its  supports  are  secured  in  the  stone  wall  except  at  the  top 
where  the  rods  extend  through  a  wooden  cornice,  the  wall 


Courtesy   of   National   Fire    Protection    Association. 


Shows  points  of  contact  (F)  between  electric  wires  and  fire  escape 
and  fused  rod  (G). 


II 


Courtesy    of    National    Fire    Protection    Association. 

Fire    Escape   at   second   floor.      Sho'ws   trolley    feeders    (A)    point   of 
contact  with  fire  escape  and   fused   rod    (B). 


12 


Courtesy   of  National   Fire    Protection    Association. 

Fire  escape  and  cornice,  fifth  floor,  showing  fused  iron  rod. 


Courtesy    of   National    Fire    Protection   Association. 

Fifth  floor  interior.     Shows  nut  and  plate   (D)   at  end  of  fused  rod 
unused  gas  pipe   (E),  roof  drain   (F). 


Courtesy    of   National    Fire    Protection    Association. 

One  of  the  several  sewer  pipes  damaged  or  fused  by  heat  generated 
by  resistance  caused  Ly  poor  conductivity  of  leaded  joints.  Note  the 
charred  sheathing. 


I  : 


Courtesy   of   National   Fire    Protection   Association. 

One  of  the  cases  where  electric  current  jumped  from  sewer  pipes  to 
adjoining  water  pipes,  fusing  both  of  them. 


i6 

and  then  into  wooden  sheathing  where  the  rod  is  held  by  an 
iron  plate  and  nut.  The  plate  and  nut  were  in  contact  with 
an  unused  gas  pipe  and  this  in  turn  wras  in  contact  with  the 
roof  drain.  The  current  from  the  feeder  passing  to  the  fire 
escape,  traveled  up  the  iron  work  to  the  fifth  floor  melting 
the  metal  at  several  points  where  the  contact  was  poor.  At 
the  fifth  floor  the  current  passed  into  the  building  over  the 
supporting  rod,  and  thence  to  the  nut,  plate,  gas  pipe  and 
sewer  piping.  The  supporting  rod  was  fused  on  the  outside 
of  the  building  at  the  fifth  floor.  The  heat  caused  by  the 
current  through  the  resistance  of  the  leaded  joints  of  the 
sewer  pipes  ignited  adjacent  wood  sheathing.  Small  fires 
were  started  in  different  parts  of  the  fifth  floor  where  sewer 
and  water  pipes  were  located,  the  leaded  joints  of  cast  iron 
sewer  pipes  being  melted.  In  several  places  where  the  water 
pipes  were  in  contact  with  server  pipes,  arcs  were  formed 
which  melted  both. 

As  an  example  of  an  arc  between  a  metal  pipe  and  an- 
other metal  pipe,  the  latter  being  grounded,  an  experience  in 
a  house,  in  the  Back  Bay  District,  Boston,  some  years  ago,  is 
of  interest.  The  house  where  the  fire  started  did  not  have 
any  electric  light  wires  in  it.  In  the  basement,  a  gas  pipe 
rested  on  a  water  pipe,  making  a  slight  contact.  Either  in 
the  ground  or  in  an  adjacent  building,  a  wire  was  in  contact 
with  a  gas  pipe.  Probably  due  to  the  resistance  of  the  joints, 
the  water  pipe  was  a  better  ground  than  the  gas  mains.  An 
"arc"  was  established  between  the  gas  and  the  water  pipe, 
which  melted  a  hole  in  the  gas  pipe,  set  the  gas  on  fire,  and 
ignited  the  woodwork  in  the  basement  ceiling. 

REQUISITES  FOR 

A  SAFE  INSTALLATION. 

That  the  installation  may  be  safe,  attention  should  be 
given  to  the  excellence  of  material,  simplicity  in  design  which 
will  permit  of  easy  inspection,  and  repairs  of  all  wiring  and 
appliances.  Special  attention  should  be  paid  to  the  mechani- 
cal execution  of  the  work,  careful  connecting,  soldering,  taping 
of  conductors,  securing  and  attaching  of  fixtures  and  the  use 
of  "approved  fittings." 

ELECTRICAL  TERMS— 
THEIR  MEANING. 

Electric  power  may  be  transmitted  by  either  direct  or 
alternating  current. 

DIRECT  CURRENT:— By  the  term  "Direct  Current" 
we  understand  it  to  refer  to  an  undirectional  current.  As  ordi- 


17 

narily  used,  the  term  designates  a  practically  non-pulsating 
current.  It  is  of  such  character  that  what  is  usually  called 
the  "direction"  of  the  current  is  always  the  same,  or,  more 
exactly,  the  magnetic  effects  of  the  current  are  not  being 
reversed. 

ALTERNATING  CURRENT:— An  alternating  current 
is  one  that  reverses  in  direction  at  regular  intervals.  Such  re- 
versals of  current  direction  are  made  automatically  by  an 
alternating-current  generator.  The  number  of  changes  in  a 
second  of  time  is  called  the  frequency,  or  cycles,  25  to  60 
being  the  commonest  now  in  commercial  use. 

Both  direct  and  alternating-current  systems  are  in  use  for 
light  and  power,  but  the  alternating-current  has  replaced 
many  of  the  direct-current  systems,  except  in  most  Street 
Railways  and  in  isolated  plants.  Where  power  must  be  trans- 
mitted to  a  considerable  distance,  alternating-current  is  used 
because  of  economic  reasons.  Incandescent  lamps,  heating 
and  other  current  consuming  devices  are  interchangeable  on 
the  two  systems-.  Motor  and  arc  lamps,  however,  require 
different  designs  for  the  two  systems.  The  same  amount  of 
current  will  heat  a  conductor  to  the  same  degree  of  tempera- 
ture, whether  it  is  a  direct  or  alternating-current  system.  As 
a  whole,  no  distinction  may  be  made  as  regards  the  fire  hazard 
between  the  two  systems,  except  that  a  direct  current  arc  is 
more  severe  than  an  alternating  current  arc.  The  same  degree 
of  care  in  workmanship,  selection  of  materials,  insulations, 
fuses  and  other  protective  devices  should  be  made  for  both 
systems. 

CURRENT: — The  practical  unit  of  electric  current  is 
called  AMPERE.  The  flow  of  water  in  a  pipe  is  measured  by 
the  quantity  of  water  that  flows  through  in  a  second,  as  I  gal. 
per  sec.,  8  gals,  per  sec.,  etc.  Similarly  the  flow  of  electricity 
in  a  circuit  is  measured  by  the  amount  of  electricity  that  flows 
along  it  in  a  second.  More  current  will,  all  conditions  being 
equal,  do  more  work,  and  will  always  cause  more  heat  in  the 
conductors  and  appliances.  Furthermore,  the  heating  effect 
in  conductors  such  as,  metals,  varies  with  "the  square  of  the 
current",  i.  e.,  if  one  unit  of  current  produces  a  certain  amount 
of  heat  in  a  wire,  twice  as  much  current  will  cause  four  times 
as  much  heat  in  the  same  wire,  three  times  the  current  will 
cause  nine  times  the  heat  and  so  on.  The  instrument  for 
measuring  current  is  called  an  ammeter. 


i8 

VOLTAGE:— The  electrical  unit  of  "PRESSURE"  is  the 
"VOLT".  A  volt  means  the  same  thing  in  speaking  of  a 
current  of  electricity  that  a  pound  pressure  does  in  speaking 
of  a  current  of  water.  Just  as  a  higher  pressure  is  required 
to  force  the  same  current  of  water  through  a  small  pipe  than 
through  a  large  pipe,  so  a  higher  electrical  pressure  is  required 
to  force  the  same  current  of  electricity  through  a  small  wire 
than  through  a  large  wire.  Since  it  is  the  voltage  which  may 
cause  electricity  to  pass  from  its  proper  path  and  seek  other 
and  perhaps  dangerous  paths,  higher  voltages  require  better 
insulation  on  wires  and  in  appliances.  The  voltage  used  thus 
becomes  an  important  factor  in  determining  the  protection 
for  safety. 

DIFFERENCE  IN  POTENTIAL:— The  voltage  (press- 
ure) between  two  points  in  an  electric  circuit,  which  points 
may  be  between  the  conductors  of  a  circuit,  or  between  one 
conductor  of  a  circuit  and  a  path  to  earth,  is  sometimes  spoken 
of  as  the  "difference  in  potential",  or  the  "drop  in  potential" 
or  merely  the  "drop",  between  those  two  points. 

Where  such  a  condition  or  difference  exists,  current  may 
pass  between  them.  We  have  said  that  "current  passing  along 
a  conductor  produces  heat"  and  when  it  jumps  between  the 
conductors  or  between  a  conductor  and  a  path  to  earth  it 
produces  an  "arc". 

RESISTANCE : — Resistance  is  the  physical  property  of 
a  material  by  virtue  of  wrhich  it  opposes  the  flow  of  an  electric 
current.  The  Ohm  is  the  practical  unit  of  resistance.  All  sub- 
stances offer  resistance  to  the  passage  of  current.  A  good 
conductor  offers  little  resistance,  while  a  poor  conductor  may 
offer  considerable  resistance  and  then  be  a  good  insulator. 
Copper  is  one  of  the  best  conductors  because  of  its  low  re- 
sistance. Iron  is  about  one-sixth  as  good  a  conductor  as  cop- 
per, and  thus  the  same  size  and  length  of  iron  wire  would 
have  about  six  times  the  resistance  of  the  same  size  of  copper. 
Wood,  when  dry,  is  a  poor  conductor,  but  a  good  insulator. 

OHM'S  LAW : — Ohm's  Law  is  a  method  of  expressing 
relationship  existing  between  the  electromotive  force,  current 
and  resistance,  and  is  practically  the  basis  of  most  electrical 
computations.  It  is  expressed  in  various  forms,  as  follows: 


• 


19 

Electromotive  Force  E 

Current  Flow——  -  or,  C=  - 

Resistance  R 

Electromotive  force  equals  the  current  flow  multiplied  by 
resistance. 

Electromotive  force  =  Current  Flow  x  Resistance,  or 
E  =  C  x  R 

Resistance  equals  the  electromotive  force  divided  by  the 
current  flow. 

Electromotive  Force  E 

Resistance  =  -  or,  R  =  — 

Current  Flow  C 

C  =  Amperes.        E  =  Volts.        R  =  Ohms. 
Electromotive    force   varies   directly   as   the   current   and 
resistance. 

Resistance  varies  directly  with  the  electromotive  force 
and  inversely  as  the  current. 

Current  varies  directly  with  the  electromotive  force  and 
inversely  as  the  resistance. 

In  this  form,  "Ohm's  Law"  applies  only  to  direct-current 
circuits  or  non-inductive  alternating-current  circuits,  the  lat- 
ter, however,  with  some  modifications. 

POWER : — The  term  "watt"  is  merely  a  unit  of  power 
and  denotes  the  power  used  when  one  volt  causes  one  ampere 
of  current  to  flow.  The  "watts"  consumed  when  any  given 
current  flows  under  any  pressure  can  always  be  found  by 
multiplying  the  current  in  amperes  by  the  pressure  in  volts. 
Thus,  if  an  incandescent  lamp  takes  0.5  amperes  when  burning 
on  a  no- volt  line,  the  power  consumed  equals  0.5  x  110  =  55 
watts.  That  is,  power  =  current  x  pressure,  or  watts  = 
amperes  x  volts."  Thus  if  the  current  in  an  incandescent 
lamp  is  Y-2  ampere  and  the  voltage  across  the  lamp  terminals 
is  no  volts,  the  power  is  55  watts.  With  alternating  current, 
the  product  of  the  volts  and  amperes  does  not  give  the  power 
consumed,  there  being  another  factor  known  as  the  power 
factor.  With  direct  current,  if  the  current,  as  read  by  a 
current  meter,  known  as  an  ammeter,  is  100  and  the  volts  are 
loo  then  the  watts  are  10,000  or  10  kilowatts.  With  alter- 
nating current,  this  power  factor  may  be  as  low  as  .60,  so  that 
the  power  instead  of  being  10,000  watts,  may  be  only  6,000  or 
6  kilowatts.  A  horse-power  equals  746  watts,  so  that  a  kilo- 
watt equals  i-%  H.  P.  and  is  expressed  as  I  K.  W. 

MULTIPLE  CONNECTION:— In  this  system  the  pres- 
sure or  voltage  is  constant,  being  that  required  for  a  single 


20 

unit.  The  total  quantity  of  current,  however,  or  the  amperes 
will  vary  directly  as  the  number  of  units  to  be  supplied.  When 
devices  are  so  connected  that  the  current  has  a  path  through 
each  separately  from  one  circuit  wire  to  another,  they  are 
connected  in  "multiple"  or  in  "parallel." 

SERIES  CONNECTION :— In  this  system  the  same 
current  traverses  in  succession,  or  in  tandem,  all  the  trans- 
lating devices.  The  electrical  pressure  or  voltage  will  vary 
directly  as  the  number  in  circuit,  the  current,  amperes,  remain- 
ing unchanged,  whether  one  or  the  whole  number  is  being 
supplied. 

CUT-OUT : — A  cut-out  is  automatic  in  its  action  and  may 
be  a  fuse  or  a  circuit-breaker.  A  fuse  is  an  element  designed 
to  melt  or  dissipate  at  a  predetermined  current  value,  and  in- 
tended to  protect  against  abnormal  conditions  of  current.  A 
circuit-breaker  is  a  device  designed  to  open  a  current  carrying 
circuit  without  injury  to  itself.  Both  in  operation  correspond 
to  the  safety-valve  on  a  steam  boiler. 

GROUND : — A  ground  may  be  either  an  intentional  or  an 
accidental  connection  between  a  part  of  an  electric  circuit  and 
the  earth,  or  any  metal  or  connecting  substance  which  are  in 
electrical  connection  with  the  earth,  such  as  water  or  gas 
pipes,  metal  work  of  buildings,  etc. 

SHORT-CIRCUIT:— This  is  a  condition  which  shortens 
the  path  below  the  normal  over  which  the  current  is  supposed 
to  flow  when  performing  its  designated  functions.  Such  a  con- 
dition is  frequently  the  result  of  accident  or  the  failure  of 
some  insulation,  and  since  it  usually  allows  excessive  currents 
to  flow,  a  short-circuit  may  be  dangerous  and  liable  to  cause 
a  fire  through  the  heating  of  the  conductor,  thus  igniting  its 
insulation,  or  a  poor  contact  which  may  cause  arcing  and 
burning  at  the  junction  of  the  conductor. 

CONSTANT-POTENTIAL  SYSTEM  :— A  constant-po- 
tential system  is  one  in  which  the  pressure,  or  voltage,  be- 
tween the  circuit  wires  is  approximately  the  same  at  all  points. 
With  such  a  system,  as  the  load  on  the  circuit  increases,  the 
current  increases. 

CONSTANT-CURRENT  SYSTEM:— A  constant-cur- 
rent system  is  one  in  which  the  current  (amperes)  is  main- 
tained approximately  constant,  regardless  of  the  number  and 
character  of  the  power  consuming  devices  on  the  circuit.  The 


21 

arc  and  incandescent  lamps  are  usually  operated  on  a  constant- 
current  system,  principally  for  convenience  of  control  and  low 
cost  of  installation. 

TWO-WIRE  SYSTEM :— A  two-wire  system  is  a  metal- 
lic circuit  formed  by  two  paralleling  conductors  insulated  from 
each  other. 

THREE-WIRE  SYSTEM:— A  three-wire  system  is  a 
double  multiple,  the  two  outside  wires  are  considered  only 
when  the  wire  is  being  figured,  as  when  the  system  is  under 
full  load  the  neutral  wire  does  not  carry  any  current.  The 
three-wire  system  has  for  its  chief  purpose  the  lessening  of 
the  cost  of  the  conductors,  in  that  three  wires  may  be  used 
instead  of  four,  and  bears  no  relation  to  the  fire  hazard. 


Courtesy  of  The  Insurance   Field. 

An  oil  insulated  transformer.  One  of  the  hazards  in  a  transformer, 
is  the  heating  of  the  coils  due  to  the  flowing  of  electrical  energy.  To 
aid  in  reducing  this  hazard  the  coils  are  immersed  in  oil  for  insulating 
purposes,  which  oil  will  ignite  at  a  reasonably  high  temperature.  In 
transformers  of  the  larger  capacity  the  oil  is  cooled  by  water  circulating 
in  a  separate  compartment. 

TRANSFORMERS :— A  transformer  is  a  stationary  in- 
duction apparatus  which  changes  electric  energy  to  electric 
energy,  through  the  medium  of  magnetic  energy  without  me- 


22 

chanical  motion.  By  the  means  of  alternating  current,  electric 
power  may  be  transmitted  from  the  generating  station  to  the 
point  where  the  power  is  to  be  utilized,  and  then  transformed 
with  small  loss  to  a  voltage  better  suited  to  motors  and  lamps. 
In  some  of  the  hydro-electric  stations,  the  alternating  current 
is  generated  at  2300  volts,  and  in  some  instances  6600  volts, 
which  voltage  is  "stepped-up",  through  transformers,  to  66,000, 
and  even  to  250,000  volts  and  is  transmitted  at  the  higher 
voltage  to  the  place  where  it  is  to  be  used,  where  it  is  "stepped 
down",  sometimes  to  several  voltages,  through  transformers, 
to  a  safe,  usable  voltage.  It  is  far  more  economical  to  transmit 
powrer  at  high  voltage  and  the  usable  current  in  many  of  our 
communities  is  generated,  by  water  power,  many  miles  away 
from  its  application. 


Part  No.  2. 
REQUIREMENTS. 

In  judging  of  installations,  it  must  be  kept  constantly  in 
mind  that  conditions  will  not  improve  after  the  wiring  and 
appliances  have  been  in  use  for  some  time.  Requirements 
are,  therefore,  made  to  anticipate  in  part  such  deterioration 
which  may  be  surprisingly  rapid  when  inferior  materials  are 
put  in  by  careless  workmen,  used  and  abused  by  those  having 
little  or  no  understanding  of  electrical  affairs  and  no  apprecia- 
tion of  the  hazard. 

The  hazards  of  electricity  were  early  recognized,  and,  on 
October  19,  1881,  the  New  York  Board  of  Fire  Underwriters 
issued  a  resolution  in  the  following  form: — 

"RESOLVED :  That  the  Committee  on  Police  and  Origin 
of  Fires  are  hereby  directed  to  notify  the  owners  and  occu- 
pants of  all  buildings  in  which  uncovered  electric  light  wires, 
or  in  which  arc  lights  with  open  bottoms  or  without  globes 
are  found,  that  the  wires  must  be  covered,  and  the  lamps 
altered  to  conform  to  the  rules  of  the  Board  within  ten  days 
from  date  of  notice,  and  request  that  the  lights  shall  not  be 
used  until  the  alterations  are  made;  and  in  case  the  altera- 
tions are  not  made  within  said  time,  the  Committee  are  hereby 
directed  to  notify  the  members  of  the  Board  of  such  failure 
and  the  companies  insuring  said  property  are  hereby  recom- 
mended to  give  notice  to  the  owners  and  occupants  of  such 
buildings  that  unless  the  request  is  complied  with,  and  the 


23 

alterations  made  within  a  reasonable  time,  that  the  insurance 
on  said  property  will  be  canceled." 

Later,  in  January,  1882,  the  same  Board  issued  simple 
rules  on  the  same  subject.  These  rules  were  not  alone  ele- 
mentary, but  indefinite,  as  well.  A  reference  to  them,  at  this 
time,  will  assist  in  showing  the  progress  made  since  that  issue 
of  rules. 

"Wires   to   be   thoroughly   and   doubly   coated   with 

some  approved  material." 

"All  wires  to  be  securely  fastened  by  some  approved 

non-conducting  material." 

"When  it  becomes  necessary  to  carry  wrires  through 

partitions  and  floors,  they  must  be  secured  against 

contact  with   metal  or  other  conducting  substances 

in  a  manner  approved  by  the  Inspector  of  the  Board." 

"The   conducting   frame   work   of   chandeliers    must 

be  insulated  and  covered  the.  same  as  wires." 

In  May,  1882,  the  National  Board  of  Fire  Underwriters 
issued  its  first  set  of  rules,  which  were  later  adopted  by  the 
Boston  Board  of  Fire  Underwriters.  The  first  rules  of  the 
New  England  Exchange  were  issued  in  August,  1885.  From 
this  date  to  the  early  part  of  1892,  rules  were  issued  by  various 
rating  organizations  and,  consequently,  different  considerably. 
Through  the  initiative  of  Mr.  C.  M.  Goddard,  Secretary  of  the 
New  England  Insurance  Exchange,  rules  were  prepared,  in 
1892,  by  the  Underwriting  Boards  in  New  England,  Middle, 
South  Atlantic  and  Gulf  States.  From  this  grew  the  Electri- 
cal Committee  of  the  Underwriters'  National  Electrical  Asso- 
ciation, and  later  in  1911  the  Electrical  Committee  of  the 
National  Fire  Protection  Association. 

While  most  of  the  members  of  the  old  Electrical  Com- 
mittee are  now  members  of  the  Electrical  Committee  of  the 
National  Fire  Protection  Association,  the  membership  of  that 
committee  has  been  enlarged,  so  that  it  now  includes  repre- 
sentatives from  the  'American  Institute  of  Electrical  Engi- 
neers, the  American  Electric  Railway  Association,  The 
National  Electrical  Contractors'  Association,  the  National 
Association,  the  National  Association  of  Electrical  Jobbers, 
the  National  Association  of  Electrical  Inspectors,  the  National 
Electric  Light  Association,  the  Chief  Electrical  Inspector  of 
the  City  of  Chicago,  also  the  Electrical  Engineer  of  the  City 
of  New  York.  To  these  'have  since  been  added  the  Electrical 


24 

Engineer  of  the  United  States  Bureau  of  Standards.  Our 
standard  now  enjoys  the  endorsement  of  the  Federal  Govern- 
ment. So  you  will  recognize  that  all  Associations  in  any  way 
interested  in  the  varied  forms  of  the  application  of  electricity, 
that  it  may  not  prove  a  menace  to  life,  limb  and  property,  have 
a  voice  in  the  making  of  the  National  Electrical  Code. 


GENERATING  AND 
SUB-STATIONS. 

The  modern  electric  generating  and  transformer  station 
is  usually  constructed  of  brick  or  concrete  walls,  with  con- 
crete floors,  concrete  roof  and  partitions  of  fire  resisting  ma- 
terial, so  that  the  amount  of  combustible  material  is  small. 

The  practice  has  been,  for  some  time,  to  erect  large  sta- 
tions from  which  the  current  is  transmitted  at  a  high  voltage 
to  a  number  of  sub-stations,  where  the  usable  voltage  is  ob- 


Courtesy    of   Grouse-Hinds    Company. 

Rear  of  switchboard  in  a  fire  proof  generating  station.  In  addition 
to  the  wide,  clear  space  between  the  wall  and  the  rear  of  the  switchboard, 
attention  is  called  to  terminal  fittings  marked  (A)  on  the  ends  of  the 
conduit.  These  terminal  fittings,  it  will  be  seen,  give  a  separately  insulated 
hole  for  each  conductor. 


25 

tained  through  transformers.  For  example,  some  of  the  cur- 
rent used  by  the  Hartford  Electric  Light  Company  is  gen- 
erated at  the  Falls  Village,  Conn.,  hydro-electric  station  and 
transmitted  at  66,000  volts,  which  is  stepped  down  to  11,000 
volts  at  sub-stations  in  Torrington,  Bristol,  Thomaston,  New 
Britain  and  Hartford.  From  the  station  at  Hartford,  the 
current  is  again  transmitted  to  a  number  of  sub-stations  and 
again  transformed  to  2300  volts.  From  these  sub-stations,  the 
current  is  now  sent  out  to  Windsor,  on  the  North ;  Manchester, 
on  the  east;  Rocky  Hill  and  Easthampton,  on  the  south  and 
Unionville  and  the  Granbys  on  the  west.  Transformers  are 
located  generally  on  the  poles  in  the  several  communities 
served  in  which  the  current  suitable  for  use  in  lamps,  motors 
and  other  appliances,  generally  110-220  volts  is  obtained 
through  being  transformed  from  the  higher  to  the  lower 
voltage. 

As  another  example,  reference  may  be  made  to  the  New 
England  Power  Company,  which  has  five  hydro-electric  sta- 
tions on  the  Deerfield  River  in  Western  Massachusetts,  and 


Courtesy  of  Turners  Falls  Power  &  Electric  Company. 

66,000  volt,  remote  control,  oil  switches  in  the  sub-station  of  the 
Turners  Falls  Power  and  Electric  Company  at  Amherst,  Mass.  From 
this  sub-station  the  distribution  of  high-potential  current  to  a  number  of 
places  in  the  Connecticut  Valley  is  controlled.  When  disconnecting  the 
conductors  of  a  high-potential  circuit  an  "arc"  of  considerable  proportions 
is  created,  to  prevent  which  the  switches  are  opened  in  oil,  hence  the 
term,  "Oil  Switches". 


26 

one  hydro-electric  station  on  the  Connecticut  River,  in  New 
Hampshire.  These  stations  are  connected  to  a  66,000  volt 
transmission  line  and  are  serving  the  electrical  needs  in  por- 
tions of  six  states,  extending  into  New  York,  on  the  west  and 
the  city  of  Providence,  on  the  east. 

The  Turners  Falls  Power  and  Electric  Company  of  Massa- 
chusetts, utilizes  the  water  power  of  the  Connecticut,  Deer- 
field  and  Green  Rivers  for  generating  electrical  energy,  having 
hydro-generating  stations  on  each  of  the  rivers  named.  The 
energy  is  transmitted  at  66,000  volts  and  is  used  in  three  of 
the  New  England  States. 

The  distribution  system  of  a  central  station  is  somewhat 
similar  to  the  blood  vessel  relations  to  the  heart  of  the  human 
system,  except  that  it  is  a  system  of  cables,  wires  and  other 
distributing  means  to  carry  electrical  energy  throughout  the 
system  from  the  main  source  of  supply.  Any  interruption  of 
this  means  of  carrying  energy  means  a  congestion  of  the 
system  which  reacts  back  on  the  entire  system.  That  this 
interruption  may  be  reduced  to  an  almost  negligible  possi- 
bility, stations  and  their  equipments  are  now  most  carefully 
planned  and  installed.  In  doing  this,  the  hazards  are  greatly 
reduced. 

It  is  also  interesting  to  note  that  the  capacities  of  the 
generating  units  are  increasing  in  size  and  potential,  and  we 
have  not,  apparently,  reached  the  limit  in  size.  In  the  first 
commercial  Edison  electric  lighting  station,  which  was  started 
in  Appleton,  Wis.,  on  August  15,  1882,  the  generating  ap- 
paratus consisted  of  one  dynamo  driven  by  water  power  and 
had  a  capacity  of  250  ten  C.  P.  incandescent  lamps.  This  was 
equal  to  I  and  *4  K.  W.  The  Hartford  Electric  Light  Com- 
pany operates  10,000  K.  W.  generators,  while  the  Chicago 
Edison  Electric  Illuminating  Company  is  using  generators  of 
20,000  K.  W.  capacity. 

In  a  modern  generating  station,  the  equipment  is  usually 
good  from  the  viewpoint  of  fire  hazard.  The  chief  troubles 
often  result  from  crowding  the  equipment  and  the  installation 
of  temporary  work,  always  conducive  to  trouble  when  it  is 
found  necessary  to  enlarge  the  capacity  of  the  plant.  Ample 
room  for  operating  and  for  inspecting  is  essential.  Accessibil- 
ity of  all  portions  of  electrical  equipment,  the  use  of  fireproof 
materials  throughout,  the  installation  of  protective  devices  of 
approved  design,  arid  of  ample  capacity  and  arrangement  by 


28 

which  any  trouble  may  be  readily  confined  to  a  limited  portion 
of  the  equipment,  are  the  chief  requisites  of  a  central-station 
equipment  from  the  viewpoint  of  the  electrical  fire  hazard. 

We  will  recognize  that  the  engineering  requirements  in 
special  cases  and  the  complexity  and  variety  of  equipments  in 
the  modern  station  render  it  manifestly  impossible  to  be 
solved  by  a  pamphlet  the  size  of  the  National  Electrical  Code. 
In  general,  generators  and  motors  of  themselves  present  less 
hazards  than  the  switchboards  with  the  mass  of  wiring  often 
found  on  them,  the  transformers  with  their  charges  of  inflam- 
mable oil,  the  electrolytic  lighting  arrestors,  or  the  large  con- 
ductors carrying  heavy  currents  and  presenting  large  surfaces 
of  inflammable  insulations.  It  is,  of  course,  extremely  essen- 
tial that  the  rules  for  safe  wiring  should  be  followed  in  all 
stations,  and  in  fact,  we  should  go  further  than  the  rules  in 
order  that  every  precaution  may  be  taken  to  avoid  interrup- 
tion of  service,  often  as  serious  with  public  corporations  as 
the  destruction  of  the  station  itself. 


GENERATORS. 

Perfect  insulation  in  electrical  apparatus  requires  that 
the  material  used  for  insulation  be  kept  dry.  While  in  the 
construction  of  generators,  the  greatest  care  is  taken  that  all 
current  carrying  parts  are  well  insulated,  still,  if  moisture 
is  allowed  to  settle  on  the  insulation,  trouble  is  almost  sure 
to  occur.  For  this  reason,  a  generator  should  never  be  in- 
stalled where  it  will  be  exposed  to  steam  or  damp  air  or  in 
any  place  where,  through  accident,  water  may  be  thrown 
against  it.  A  location  under  steam  or  water  pipes  or  close  to 
an  outside  window  should  be  avoided.  No  combustible  ma- 
terial should  be  permitted  near  a  generator  as  the  hot  particles 
of  carbon  from  the  brushes  can  ignite  dust  in  grain  elevators, 
wood-working  rooms  and  other  dust  of  an  inflammable  nature. 
A  generator  should  be  so  located  as  to  provide  for  ventilation, 
since  the  cooler  a  machine  can  run,  the  more  efficient  it  will  be. 

The  frames  of  generators  operating  at  a  high  potential,  in 
excess  of  550  volts,  should  be  grounded,  since  it  is  not  practi- 
cal to  attempt  to  insulate  them.  Generators  operating  at  a 
potential  less  than  550  volts  should  either  have  their  frames 
insulated  from  earth  or  be  permanently  and  effectively 
grounded. 


30 

In  our  former  lecture  it  was  stated  that  a  constant- 
potential  system  was  a  system  in  which  the  potential  (voltage) 
was  always  the  same,  the  current  increasing  with  the  load. 
It  is,  therefore,  necessary  for  some  form  of  protective  device 
to  be  provided  so  that  these  machines  may  not  be  overloaded. 

CONDUCTORS. 

All  wiring  in  a  generating  or  sub-station  should  be  in- 
stalled in  the  most  substantial  manner,  and  care  and  attention 
should  be  given  to  simplicity  and  orderliness  of  arrangement. 
It  should  be  readily  renewable  and  accessible.  All  conductors 
should  have  ample  current-capacity,  and  in  their  installation, 
care  must  be  given  to  securing  excellent  insulation  and  reliable 
supports.  Special  regard  should  be  given  to  the  possibility  of 
injury  to  conductors  by  tools,  belts,  ladders  or  from  any  other 
means  which  may  cause  a  gradual  wear  of  the  insulation.  The 
conductors  from  generators  to  switchboards,  resistances  or 
other  instruments  and  thence  to  outside  lines : 

Must  be  in  plain  sight  or  readily  accessible,  or  if  properly 
insulated,  lead  encased  cable  may  be  laid  in  approved  non- 
combustible  conduits. 

Where  a  number  of  wires  are  brought  close  together,  as 
is  generally  the  case  in  dynamo  rooms,  especially  on  or  about 
switchboards,  they  must  be  surrounded  wTith  a  tight,  non- 
combustible  outer  cover  (not  to  apply  to  low  tension  bus 
bars). 

Wires  shall  be  carried  as  direct  as  possible  from  the 
switchboard  to  the  point  at  which  they  leave  the  building, 
and  if  leading  to  aerial  lines  shall  incline  downward  to  prevent 
the  entrance  of  rain  along  the  wires. 

Must  be  separated  from  contact  with  floors,  partitions  or 
walls  through  which  they  pass,  by  non-combustible,  non- 
absorptive  insulating  tubes  such  as  glass  or  porcelain,  with 
distance  between  sufficient  to  prevent  possible  contact.  Must 
have  no  air  space  where  they  pass  through  floors  from  base- 
ment to  switchboard  other  than  that  of  the  insulating  tubes. 

Other  than  for  exciters  all  constant  potential  leads,  with 
the  exception  of  the  neutral  of  a  three-wire  system  and  the 
grounded  side  of  a  railway  system,  must  be  protected  by  ap- 
proved automatic  cut-outs  at  the  station. 

SWITCHBOARDS. 

The  danger  of  fire  at  switchboards  lies  in  the  large  num- 
ber of  wires  usually  concentrated  on  them,  and  the  use  of 


devices  and  appliances  which  are  possible  sources  of  fire.  A 
switchboard  may  be  made  of  hard  wood  in  skeleton  form,  in 
which  case  all  switches,  cut-outs,  instruments,  etc.,  must  be 
mounted  on  non-combustible  insulating  bases.  Switchboards 
are  more  generally  made,  however,  of  slate  or  marble,  free 
from  metallic  veins.  If  metallic  veins  are  not  guarded  against, 
they  may  cause  great  leakage  of  current,  which  will  manifest 
itself  in  heating  the  slate  or  marble.  The  slate  or  marble  is 
supported  on  metal  frames. 


Courtesy  of  Turners   Falls  Power  &  Electric  Company. 

View  of  the  switchboard  operating  gallery  in  the  high-potential 
generating  station  of  the  Turners  Falls  Power  and  Electric  Company, 
Montague  City,  Mass. 

A  switchboard  should  be  located  well  away  from  combus- 
tible material  and  should  be  open  on  all  sides,  that  every  part  of 
the  switchboard  and  its  equipment  may  be  accessible.  There 
should  be  a  space  of  at  least  three  feet  between  the  top  of  the 
switchboard  and  the  ceiling,  in  order  to  lessen  the  danger  of 
communicating  fire  to  the  ceiling.  When  the  switchboard  is 
back  connected,  there  should  be  a  clear  space  of  at  least 
eighteen  inches.  Every  precaution  must  be  taken  to  keep 
moisture  or  water  from  a  switchboard,  since  this,  of  course, 
will  result  in  a  short  circuit,  as  we  are  forced  to  have  more  or 
less  unprotected  contacts.  While  the  front  of  the  switchboard 
is  the  operating  side,  the  rear  is  the  part  where  trouble  is 


32 

more  likely  to  occur.  The  back  of  the  switchboard  should, 
therefore,  be  easily  accessible  and  neatness  of  arrangement 
and  reliable  supports  for  all  conductors  be  imperative.  No 
makeshifts  should  be  permitted  on  a  switchboard  under  any 
conditions.  Absolute  cleanliness,  especially  behind  the 
switchboard,  should  be  insisted  upon.  I  can  recall  two  fires, 
where  the  switchboards  were  located  near  windows,  caused 
by  snow  being  blown  through  broken  lights  of  glass. 


Courtesy  of  Turners  Falls  Power  &  Electric  Company. 

Bench  board  and  operating  desk  in  the  generating  station  at  Montague 
City,  Mass. 

RESISTANCES  AND 
EQUALIZERS. 

Must  be  of  approved  type  and  not  located  in  proximity 
to  combustible  material.  Insulated  wire  for  connection  be- 
tween a  rheostat  and  its  contact  plate  should  have  flame-proof 
insulation.  These  devices,  which  are  used  in  great  variety  of 
sizes  and  designs,  resemble  the  valve  of  a  steam  engine,  in 
that  they  are  regulators.  In  central  stations  where  current  is 
furnished  over  a  large  area,  there  is  on  some  of  the  circuits, 
especially  the  long  ones,  a  considerable  "drop",  or  loss  of 
potential.  In  order  to  keep  the  voltage  at  the  point  of  supply 
on  these  circuits  at  the  proper  value,  the  voltage  at  the  station 
must  be  raised.  This,  in  turn,  causes  the  voltage  on  these 
circuits  near  the  dynamo  to  become  excessive.  Equalizers, 


Courtesy  of  Trumbull  Electric  Manufacturing  Co. 

A  marble  switchboard,  well  arranged  with  remote  control,  high- 
potential  oil  switches  on  extreme  left,  automatic  circuit  breakers,  knife- 
switches,  meters  and  equalizers,  located  on  the  face  of  the  switchboard. 
This  switchboard  is  well  away  from  the  brick  wall,  thus  making  the  rear 
of  it  accessible.  The  ends  are  protected  by  substantial  wire  grills,  to 
prevent  using  the  space  back  of  the  switchboard  for  storage  purposes. 
This  switchboard  is  in  the  basement  of  the  Amoskeag  Bank,  New 
Hampshire. 


34 

which  are  large  resistances  generally  constructed  of  iron  or 
strips  and  capable  of  carrying  a  heavy  current,  are  connected 
in  the  circuits  and  adjusted  at  such  resistances  as  to  make  the 
voltage  at  the  various  points  of  supply  uniform.  They  are 
generally  too  heavy  to  mount  on  the  switchboard  and  are, 
usually,  mounted  above  the  switchboard  on  non-inflammable 
material.  They  are,  in  reality,  sources  of  heat  and  should  be 
so  arranged  and  installed  that  even  if  overheated  they  cannot 
cause  injury  to  surrounding  objects.  The  burning  out  of  a 
rheostat  may  cause  a  flame  or  flash,  and  oftentimes  melted 
solder  or  other  material  is  thrown  off,  which,  if  it  comes  in 
contact  with  combustible  material,  will  start  a  fire. 


LIGHTNING  ARRESTERS. 

The  purpose  of  these  protective  devices  is  to  prevent 
lightning,  or  external  high-voltage  currents  from  foreign 
circuits  entering  the  station  and  causing  fire  or  damaging  ma- 
chinery and  instruments.  Lightning  cannot  be  "stopped"  but 
may  be  diverted  to  the  earth.  They  should  be  connected  to 


Courtesy  of  The   Insurance   Field. 

The  latest  form  of  lightning  arresters  which  involves  an  entirely  new 
principle  for  protection  against  lightning,  is  that  known  as  the  Electrolytic 
or  Aluminum  Arrester.  This  arrester  is  used  chiefly  on  high  tension 
transmission  lines.  The  above  illustration  is  a  cross  section  view  of  the 
device,  the  "inverted  dishes"  are  called  aluminum  cones.  Arresters  of 
this  type  should  preferably  be  installed  out  of  doors. 


35 

every  overhead  circuit  connected  with  the  station.  The  object 
of  a  lightning  discharge  from  its  beginning  is  to  find  its  way 
to  earth  and  if  it  can  reach  it  more  easily  by  some  other  path 
than  by  first  going  to  the  generator  it  will  ordinarily  take  that 
direction.  Electricity,  no  matter  what  its  character  may  be, 
will  choose  the  path  of  least  resistance. 


A  lightning  Arrester  of  the  Magnetic  Blow-Out  Type  has  for  its 
purpose  the  protection  of  circuits  and  apparatus  against  lightning  and 
other  abnormal  potential  rises  of  short  duration.  In  the  above  illustration 
A  and  B  are  two  copper  'wings  separated  from  each  other ;  the  lightning 
coming  in  over  the  line  B,  jumps  the  narrow  air  space  to  A,  from  which 
it  passes,  by  a  wire  connected  to  a  water  pipe  or  other  proper  earthing 
provision  direct  to  ground.  The  electro  magnets,  C  and  D,  are  excited 
by  a  current  from  the  generator  and  serve  to  "blow-out"  the  arc  between 
the  wings  so  that  the  generator  current  cannot  follow  to  earth.  The  air 
space  between  the  wings  where  they  come  nearest  together  is  made  great 
enough  to  prevent  the  generator  current  from  jumping  it  of  its  own 
initiative,  it  being  'well  known  just  how  far  through  air  currents  at 
different  voltages  can  jump;  but  if  the  arc  is  first  established  the  gases 
generated  greatly  lower  the  resistance  of  the  path  across  the  air  space  and, 
were  some  means  not  provided  for  extinguishing  this  arc  formed  by  the 
lightning  discharge,  it  would  be  maintained  by  the  generator  current  after 
the  lightning  discharge  had  ceased  and  therein  is  the  main  fire  hazard 
from  this  apparatus. 

In  order  to  increase  the  difficulties  of  the  lightning  dis- 
charge reaching  the  generators,  it  is  customary  to  introduce 
directly  in  the  wire  at  some  point  between  the  arrester  and 
the  machine  a  coil  of  wire  known  as  "reactance"  or  "choke 
coil",  the  object  of  which  is  to  choke  this  discharge  back  from 
the  machine  to  the  easier  path  provided  through  the  arrester. 
While  there  are  a  number  of  types  of  arresters,  the  main 
principle  embodied  is  common  to  them  all ;  that  is,  a  resistance 
and  an  air  gap  across  which  the  current  must  jump  to  reach 
the  earth.  When  the  discharge  jumps  the  air  gap,  an  arc  is 
formed  and  if  the  arrester  is  not  designed  to  promptly  ex- 
tinguish this  arc,  the  generator  current  is  likely  to  follow  and 


36 

if  there  is  anything  combustible  in  the  immediate  vicinity,  fire 
may  readily  ensue. 

The  arresters  must  always  be  connected  with  a  thor- 
oughly good  and  permanent  ground  connection,  and  this 
ground  wire  must  be  run  as  free  as  possible  from  kinks,  coils 


Courtesy   of  The   Insurance   Field. 

Choke  coil   for   the   purpose   of  diverting   lightning   discharges    from 
the  line  to  the  ground. 

and  sharp  bends.  The  ground  connection  should  not  be  con- 
nected to  gas  pipes,  as  there  is  always  a  liability  of  a  very 
severe  discharge,  which,  with  a  gas  service,  may  result  in 
melting  the  gas  pipe  and  igniting  the  escaping  gas,  thus  caus- 
ing an  explosion  or  a  fire. 

TESTING  OF 
INSULATION  RESISTANCE. 

Except  where  circuits  are  intentionally  and  permanently 
grounded,  a  "leak"  to  "ground"  may  be  the  cause  of  arcs  at 
any  point  in  the  system  which  may  be  dangerous.  The  amount 
of  leak  varies,  but  is  always  dependent  on  the  insulation  re- 
sistance. Where  a  small  amount  of  wire  is  well  installed,  the 
leak  should  be  very  small,  but  in  the  case  of  large  installations 
or  where  the  wiring  has  been  poorly  done,  the  flow  of  current 
to  ground  or  between  wires  of  opposite  polarity  may  become 
quite  large.  Wires  lying  on  pipes  or  on  damp  woodwork, 
crossed  wires  or  live  parts  of  apparatus  mounted  on  wooden 
blocks,  all  tend  to  cut  down  the  insulation  resistance  and  in- 
crease the  leak.  The  effects  of  poor  insulation  are;  First,  it 
represents  a  useless  loss  of  current,  and  second,  and  more 
important,  it  means  a  possible  cause  of  fire.  All  circuits, 
therefore,  should  be  so  arranged  that  they  may  be  tested  as 
to  their  freedom  from  grounds  and  leaks. 


37 


3»t  iron  v,iter  pipe  '  /'  S     <,, . 77  ,  .' " ^T ',  fT 


Courtesy    of   The   Associated    Factory    Mutual    Fire   Ins.    Co. 

Method  of  connecting  the  lightning  arrester,  choke-coil,  and  ground 
wire  to  outside  line  and  earth ;  also  showing  an  oil  switch  and  line  to  mill. 


An  oscillatory  discharge  of  lightning  taken  by  the  author  in  the  city 
of  Hartford,  July  18,  1908. 


33 

Part  No.  3. 
ELECTRIC  MOTORS. 

To  trace  the  history  of  the  electric  motor  would  require  a 
volume  in  itself,  and  that  too,  one  of  no  mean  dimensions.  The 
early  history  of  invention  in  the  line  of  electric  motors  in- 
clude a  number  of  well  known  names,  the  most  prominent  of 
which,  as  I  now  recall  them,  are  Jacobi,  Ritchie,  Wilde,  Dai- 
Negro,  and,  coming  down  to  the  present  day,  the  well  known 
inventors  whose  successful  electric  motors  are  now  occupying 
so  important  a  field  in  various  lines  of  work. 

I  am  unable  to  recall  an  electric  device  which  is  so  inti- 
mately related  to  our  every  day  industrial  life  as  the  electric 
motor.  Its  development  and  popular  use  has  increased  far  be- 
yond my  ability  to  relate.  They  are  now  very  generally  used 
in  manufacturing  plants  of  all  kinds ;  they  are  to  be  found  on 
the  farms,  far  back  in  the  country,  and  in  our  homes  perform- 
ing simple  tasks  in  an  economic  manner.  Their  use  is  in- 
creasing, as  is  also  their  opportunity,  due  largely,  I  believe, 
to  the  many  hydro-electric  developments,  wTith  their  far 
reaching  transmission  lines. 

Portable  motors  of  small  size  have  come  into  general  use 
for  drills,  portable  tools,  vacuum  cleaners,  washing  machines, 
sewing  machines,  massaging  appliances  and  many  other  pur- 
poses where  their  cleanliness,  economy  and  adaptability  to  all 
service  recommends  them.  These  portable  motors,  however, 
do  not  come  under  the  rules  prescribed  for  stationary  motors, 
though  their  use  involve^, similar  hazards  and  some  others 
peculiar  to  themselves. 

In  some  respects,  a  motor  should  receive  the  same  con- 
sideration as  a  generator,  in  that  it  should  be  located  in  a 
clean,  dry  place,  although  motors  are  so  constructed  that  they 
can  be  operated  .out  of  doors  and  even  where  moisture  is 
present.  Except  when  unavoidable,  motors  should  never  be 
located  in  a  dusty  or  linty  place,  and  when  so  located  should 
be  enclosed  in  a  separate  room,  which  room  should  be  largely 
of  glass,  so  that  the  condition  of  the  motor  may  be  noted 
from  the  outside. 

We  are  now  having  a  number  of  2300  volt  installations 
for  power  and  the  requirements  for  these  are  greatly  different 
from  those  for  motors  which  operate  at  a  potential  of  550 
volts  or  less.  The  wiring  for  motors  of  the  lower  potential 
may  be  what  is  termed  "open  work",  which  consists  of  ex- 


39 

posed  wires  supported  on  porcelain  cleats  or  knobs.  When 
we  purpose  using  motors  of  the  higher  potential,  however,  the 
wiring  must  be  in  multiple  conductor,  lead-sheathed,  cable, 
installed  in  an  approved  metal  conduit,  unless  the  installation 
be  in  a  central  or  sub-station  where  the  men  employed  would 
be  familiar  with  the  life  hazards  involved,  when  the  installa- 
tion may  be  in  open  wiring.  The  lead  sheathing  of  the 
multiple  conductor  cable  and  the  metal  conduit  must  be 
effectively  grounded,  that,  in  event  of  either  becoming  of  a 
potential,  the  current  may  be  shunted  to  earth. 


Courtesy    of    Crouse-Hinds    Company. 

The  application  of  electricity  in  cotton  mills  has  been  the  subject  of 
study  by  Electrical  Engineers  for  many  years.  This  is  because  of  the 
deposits  of  lint  which  settle  on  all  wires,  switches,  cut-outs  and  other 
fixtures,  ready  to  burst  into  flame  at  the  first  spark.  In  the  above  method 
of  installation  all  live  current-carrying  parts  are  well  protected  from 
dust  and  lint  as  well  as  from  mechanical  injury. 

The  conduit  system  must  be  connected  to  the  motors, 
starting  devices,  switches,  circuit-breakers  and  all  appliances, 
that  there  will  be  no  exposed  wiring.  There  are  no  motors  in 
commercial  use  between  550  volts  and  2200  volts,  and,  when 
making  the  rules,  it  was  not  thought  too  much  to  ask  that  a 


40 

form  of  construction  and  installation  which  would  provide  for 
the  greatest  amount  of  protection  to  the  wires  and  the  several 
appliances  should  be  provided. 

Care  should  be  exercised  at  all  times  to  have  the  wires  of 
the  motor  circuits  of  sufficient  size  that  they  can  care  for  the 
starting  current,  which  is  always  in  excess  of  the  full  running 
load.  For  this  reason  the  rule  requires  that  the  conductors 
carrying  the  current  of  only  one  motor  must  be  of  sufficient 
size  to  carry  a  current  at  least  25  per  cent,  greater  than  for 
which  the  motor  is  rated.  This  requirement  applies  more 
especially  to  motors  connected  to  direct  current  systems.  For 
motors  connected  to  alternating-current  circuits,  where  the 
starting  load  is  some  times  350  per  cent,  greater  than  the  full 
running  load,  attention  must  be  given  to  proper  protection,  in 
the  form  of  fuses  or  circuit-breakers  of  the  circuit  wires. 
Where  the  conductors  "under  the  rule  would  be  overfused  in 
order  to  provide  for  the  starting  current,  as  in  the  case  of 
many  of  the  alternating  current  motors,  the  conductors  must 
be  of  such  size  as  to  be  properly  protected  by  these  larger 
fuses. 

The  use  of  motors  operated  on  current  taken  either  from 
the  trolley,  or  from  a  generator  directly  supplying  the  trolley 
system,  is  prohibited,  owing  to  the  fact  that  the  trolley  system 
is  always  a  grounded  system  and  the  current  is  too  dangerous 
to  bring  inside  buildings.  One  side  of  the  circuit  being 
normally  grounded,  there  is  always  a  tendency  for  the  current 
that  enters  the  building,  if  opportunity  offers,  to  find  some 
path  to  earth  and  return  to  the  generator  by  that  path.  This 
increases  the  fire  hazard.  These  circuits  are  also  more  likely 
to  suffer  from  lightning.  In  street  railway  repair  shops,  of 
course,  these  motors  are  permitted  because  the  trolley  current 
is  one  of  the  hazards  inherent  to  the  risk,  and  this  is  taken  into 
consideration  in  classifying  the  risk. 

The  protective  devices  for  motors  are  especially  neces- 
sary, since  the  load  is  usually  throwrn  on  or  off,  and  this  load 
may  be  in  excess  of  that  for  which  the  motor  was  designed. 

These  protective  devices  are  either  in  the  form  of  fuses 
or  circuit  breakers,  both  being  automatic  in  operation. 
Circuit-breakers  are  to  be  recommended,  as,  when  the 
breaker  opens,  the  service  can  more  easily  be  put  again  into 
commission.  A  reference  to  the  rule  will  show  that  the  start- 
ing device  for  the  motor  must  be  located  in  sight  of  the 


motor,  except  where  special  permission  is  given  to  deviate 
from  this  rule.  As  can  be  readily  understood,  it  is  not  usually 
considered  safe  for  a  motor  to  be  started  with  the  operator 
not  in  sight  of  the  motor,  in  the  event  of  there  being  any 
derangement  of  the  shafting,  pulleys,  belting,  etc.,  or  should 
the  motor  fail  to  start  and  thus  heat,  the  operator  will  be  in  a 
position  to  disconnect  the  circuit,  through  the  switch,  before 
serious  damage  has  been  done. 


Courtesy    of    Crouse-Hinds    Company. 

Method  of  installing  conductors  in  conduit  to  a  motor  with  the  use 
of  a  floor  flange  which  adds  rigidity  to  the  conduit. 

A  starting  device  is  an  appliance  for  limiting  the  current 
strength  during  the  starting  of  the  motor  by  inserting  a  re- 
sistance in  series  with  the  armature.  For  motors  connected 
to  direct  current  systems  a  starting-box,  or  rheostat,  is  used, 
while  for  motors  connected  to  alternating  current  systems,  the 
starting  device  is  somewhat  different  and  has  somewhat  the 
form  of  a  transformer. 


Courtesy   of   Trumbull   Electric   Manufacturing   Company. 


Installation  of  a  starting  rheostat  upon  a  slate  slab,  thus  protecting 
combustible  material  from  the  heat  in  the  starting  device — the  protective 
fuses  and  starting  switches  are  on  the  left  of  the  rheostat. 

In  a  former  lecture,  reference  was  made  to  the  need  of 
treating  resistance,  or  rheostats,  as  being  sources  of  heat  and 
should  be  located  away  from  combustible  material.  This  is 
usually  done  by  mounting  the  rheostat  on  a  continuous  piece 
of  slate  or  marble,  the  slate  or  marble  then  independently  se- 
cured to  the  wall,  never  using,  howrever,  the  same  screw  for 
attaching  both.  Motor  starters  for  direct  current  motors 
should  also  be  provided  with  a  no-voltage  release.  This  in 
its  simplest  form  is  a  magnet  across  the  line  which  holds  the 
lever  arm  of  the  rheostat.  When  the  current  fails,  the  lever 
arm  is  drawn  back  by  a  coiled  spring.  Another  device,  known 
as  the  "overload  release"  is  frequently  attached  to  a  rheostat, 
its  intended  office  being  to  release  the  arm  of  the  rheostat 
should  the  load  become  greater  than  that  for  which  it  was 
designed. 

I  have  mentioned  that  the  starting  devices  for  alternating 
current  motors  differed  from  those  for  the  direct  current 
motors.  These  alternating  current  devices  are  called  auto- 
starters.  Instead  of  an  ohmic  resistance,  an  inductance  is 
used  to  keep  the  current  from  attaining  excessive  value  while 
the  motor  is  coming  up  to  speed.  These  devices  are  generally 
so  constructed  that  the  operator  cannot  leave  them  in  a  posi- 
tion where  any  current  passes  through  the  starting  device. 
They  are  usually  oil  immersed,  so  that  in  case  of  trouble  there 
is  considerable  combustible  material.  In  general,  motor 


43 


Courtesy   of  Commissioner  James   E.   Cole,   Wire   Department,  Boston,   Mass. 


Rheostat  used  in  connection  with  motor  was  defective,  the  greater 
portion  of  the  coils  being  open-circuited,  motor  not  taking  current  until 
contact  finger  was  on  next  to  last  button  of  contact  points.  Motor  was 
started  shortly  before  fire  was  discovered,  and  excessive  sparking  at 
commutator,  due  to  defective  condition  of  rheostat,  occurred.  Fire  was 
caused  by  these  sparks  igniting  oil,  lint  or  other  inflammable  material  in 
vicinity  of  motor. 


44 


5 t. /ire 


pheostat  properly  mounted. 


starters,  either  for  direct  current  or  alternating  current  cir- 
cuits, present  the  hazards  of  switches  and  possibly  overheated 
coils,  and  must  be  so  considered  and  treated  accordingly. 


RAILWAY 
POWER  STATIONS. 

In  the  city  of  Meriden,  Conn.,  years  ago,  there  was  an 
ungrounded  trolley  system  which  had  a  double  overhead 
trolley.  Such  a  system  has  been  advocated  and  even  tried  in 
several  other  places,  but,  in  each  effort,  operating  difficulties 
presented  themselves.  The  system  had  two  overhead  wires, 
while  the  cars  had  double  trolleys.  With  this  arrangement, 
the  tracks  had  no  part  in  the  return  circuit,  and  the  current 
was  kept  free  from  ground.  Practically  all  of  the  railway 
power  stations  now  operate  with  a  ground  return,  so  that  in 
case  of  a  ground  on  any  feed  wire,  we  will  have  a  dead  short- 


45 

circuit.     For  this  reason  and  on  account  of  the  load  carried, 
the  protection  device  must  be  of  the  circuit-breaker  type. 

STORAGE  OR 
PRIMARY  BATTERIES. 

Batteries  of  large  size  are  now  to  be  found  in  common 
use.  These  are  practically  always  storage  batteries,  that  is, 
batteries  which  are  recharged  by  having  current  from  a  gen- 
erator supplied  to  them  from  time  to  time.  It  always  gives 
out  direct  current  in  the  reverse  order  from  which  it  is 
charged.  Primary  batteries  are  very  limited  in  their  capacity 
and  are  used  chiefly  for  signaling  systems  when  current  from 
generators  is  not  available.  Storage  batteries  are  now  found 
in  the  high  voltage  generating  and  transmission  stations 
for  the  remote  control  of  the  hjigh  voltage  oil  switches  and 
circuit  breakers.  They  are  also''used  to  assist  a  station  during 
what  is  called  the  "peak  load".  They  are  also  used  in  most 
of  the  telephone  exchanges  and  on  many  of  the  automatic 
fire  alarm  systems.  A  storage  battery  may  very  properly  be 
called  a  reservoir  of  energy,  capable  of  producing  trouble  if 
their  output  is  not  properly  controlled. 

The  action  of  the  current  in  charging  the  battery  liberates 
at  time  large  quantities  of  hydrogen  and  oxygen,  and  if  these 
should  accumulate  in  the  right  proportions  they  would  form 
an  explosive  mixture  which  might  be  exploded  by  any  acci- 
dental spark,  for  this  reason,  therefore,  storage  battery  rooms 
must  be  thoroughly  ventilated.  As  practically  all  of  the 
batteries  in  use  contain  sulphuric  acid,  it  is  necessary  to  pro- 
vide in  the  battery  rooms  for  the  protection  against  corrosive 
vapors.  The  water  and  acid  in  the  rooms  require  that  the 
wires  should  be  especially  well  insulated. 

TRANSFORMERS. 

At  this  time,  we  are  to  consider  the  fire  hazards  intro- 
duced by  transformers  as  they  concern  central  and  sub-sta- 
tions, in  which  stations  the  transformers  must  be  so  placed 
that  smoke  from  the  burning  out  of  the  coils  or  the  burning 
over  of  the  oil  (where  oil  filled  cases  are  used)  could  do  no 
harm.  Most  of  the  transformers  used  in  central  or  sub-sta- 
tions contain  oil  for  insulation  and,  sometimes,  for  cooling. 
As  the  amount  of  oil  in  large  transformers  is  considerable,  and 


46 

as  it  will  cause  a  very  hot  fire,  should  it  become  ignited,  it  is 
necessary  to  so  locate  these  transformers,  that  in  case  of  a 
burn-out,  the  burning  oil  or  insulation  will  not  endanger  the 
balance  of  the  plant.  In  central  stations,  where  there  is  other 
equipment,  the  transformers  are  generally  placed  in  trans- 
former rooms,  which  rooms  should  be  well  ventilated  to  the 
outside  air  to  prevent  the  accumulation  of  explosive  vapors, 
which  may  be  given  off  from  the  oil  when  hot,  and  to  facilitate 
keeping  the  room  cool,  thus  preventing  overheating  of  the 
transformers.  These  rooms  should  be  of  fire  resisting  material. 


Courtesy  of  Turners  Falls  Power  &  Electric  Company. 

66,000  volt  transformers  used  by  the  Turners  Falls  Power  and 
Electric  Company  in  its  outdoor  station  at  Chicopee,  Mass.  The  supply 
of  electrical  energy  for  these  transformers  is  from  the  hydro-electric 
generating  station  on  the  Connecticut  River  at  Montague  City,  Mass. 


Provision  should  be  made  to  prevent  the  spread  of  the 
burning  oil,  also  for  quickly  emptying  the  transformer  cases 
of  oil  through  the  means  of  quick-acting  valves  which  can  be 
operated  outside  of  the  transformer  rooms.  In  many  of  the 
high-potential  transmission  companies,  the  large  capacity 
transformers  are  now  located  out-of-doors  and  are  called 
"out-door  stations",  in  which  stations  care  should  be  taken  to 
prevent  burning  oil  from  flowing  to  any  buildings  which  may 
be  near. 


47 

OUTSIDE  WORK. 

The  rules  for  Outside  Work  are  intended  to  safeguard 
risks  which  may  be  exposed  to  hazards  of  outside  electrical 
conditions  and  are  to  be  applied  to  all  systems  and  voltages, 
but  are  not  to  be  considered  for  installations  for  Light,  Heat 
or  Power  protected  by  the  service  cut-out  and  switch,  which 
will  be  explained  during  a  later  lecture.  There  are  several 
ways  in  which  outside  wires  may  be  a  menace  to  buildings. 
First. — By  producing  abnormal  conditions  on  the  inside 
wiring,  as  when  one  wire  becomes  grounded,  there  already 
being  a  ground  on  another  wire  of  this  circuit  inside  the 
building:  A  short  circuit  of  wires  outside  causing  the  fuses 
inside  to  blow.  Special  care  should  be  taken  to  prevent  a 
short-circuit  between  open  wires  occurring  close  enough  to 
woodwork  of  buildings  to  ignite  it.  Second. — By  the  crossing 
of  a  high-potential  wire  with  a  low-potential,  the  cross  being 
when  one  wire  of  the  high  tension  circuit  touches  or  comes 
in  contact  with  a  wire  of  the  low-potential  circuit.  As  an 
example,  I  might  cite  the  case  of  a  2300  volt  circuit  in  contact 
with  a  no  volt  circuit,  which  no  volt  circuit  was  intentionally 
grounded  on  a  water  pipe  in  the  building  which  it  served. 

This  cross  was  made  possible  by  the  sag  of  the  wires  on 
the  pole  line  during  a  heavy  snow  and  rain  storm.  The  other 
wire  of  2300  volt  system  was  grounded  on  the  limb  of  a  tree 
which  was  heavily  covered  with  wet  snow.  This  established 
a  high  potential  cross  and  the  wires  of  the  low  potential  cir- 
cuit rose  to  the  higher,  2300  volt  circuit.  There  were  arcs 
established  in  the  fuses  which  blew,  and  the  fixtures  and 
sockets,  which  arcs  caused  a  number  of  small  fires  throughout 
the  one  building,  there  being  but  one  building  on  that  sec- 
ondary system. 

Another  example  is  that  of  a  telephone  wire  becoming 
crossed  with  a  wire  of  a  lighting  circuit,  either  of  low  or  high 
potential,  and,  unless  the  telephone  was  properly  protected 
where  it  entered  the  building,  arcs  or  grounds  would  then  be 
easily  established  and  fire  ensue  as  a  result.  Third. — By  wires 
coming  in  contact  with  buildings,  starting  arcs  or  grounds 
through  damp  woodwork  or  conductors,  flashings,  etc. 


48 

CARE  IN 
CONSTRUCTION. 

For  these  reasons,  it  is  extremely  important  for  all  out- 
side wires  to  be  run  in  a  substantial  and  careful  manner, 
especially  so  as  not  to  interfere  with  the  operations  of  a  Fire 
Department  in  the  time  of  a  fire.  We  sometimes  find  men 
who  are  careless  in  that  particular,  seeking  to  construct  the 
outside  lines  in  the  easiest  possible  manner,  regardless  of 
looks  or  safety.  We  can  now  appreciate  the  placing  of  all 
outside  wires  underground,  the  electric  light  and  power  cir- 
cuits installed  in  one  set  of  conduits,  and  wrhat  is  called 
signaling  wires  in  another  set  of  conduits,  both  systems  of 
conduits  being  independent  of  the  other,  each  system  being 
provided  with  separate  manholes.  These  signaling  systems 
include  the  telephone,  the  telegraph,  district  messenger,  fire 
and  police  alarm,  clock  and  burglar  alarm  systems.  The 
underground  system  is  expensive  to  install  and  may  only  be 
found  in  cities  of  the  larger  size. 

The  next  best  method  is  one  we  sometimes  see,  that  of 
having  one  set  of  poles  for  the  electric  light  and  power  wires 
and  another  set  for  the  signaling  wires,  thus  keeping  the 
several  systems  separate.  The  objection  to  a  system  of  this 
character  is  largely  one  of  appearance,  it  requiring  two  sets 
of  pole  lines,  one  on  each  side  of  the  street.  It  is  a  general 
practice,  however,  when  the  wires  are  not  underground,  to 
run  both  the  electric  light  and  power  wires  and  the  wires  of 
the  signaling  systems  on  the  same  set  of  poles.  In  such 
cases,  the  signaling  wires  should  not  be  placed  on  the  same 
cross-arm  with  the  electric  light  and  power  wires. 

OUTSIDE  WIRES. 

Line  wires  may  have  either  rubber  insulating  or  weather- 
proof covering.  The  standard  practice  has  been,  however,  to 
use  the  latter,  which  consists  of  three  cotton  braids,  each 
thoroughly  impregnated  with  a  water-proof  compound.  This 
covering  is  depended  upon  for  accidental  contact  but  not  for 
insulation  proper.  The  conductors  for  the  extra-high 
potential  transmission  lines,  however,  are  without  covering 
of  any  nature,  but  such  lines  are  not  to  be  seen  in  congested 
areas,  except  they  be  upon  very  high  poles,  when  the  lines  are 
at  the  top  out  of  reach  of  linemen  when  working  on  other 
lines.  All  tie  wires,  as  at  insulators,  must  have  an  insulation 


49 

equal  to  that  of  the  wires  they  confine.  While  rubber  insula- 
tion may  be  used,  it  is  much  more  expensive  and  in  a  few 
years  would  be  no  better  than  weather-proof. 

It  is  the  general  practice  to  support  the  outside  wires  on 
glass  or  porcelain  insulators  at  least  I  foot  apart  on  pole  line 
cross-arms.  These  insulators  are  called  "petticoats"  and  will 
nearly  always  have  a  dry  space  underneath  their  lower  edges, 
and  even  if  not  dry,  the  length  of  the  path  offered  to  the 
current  escaping,  over  the  wet  surface  is  so  great  that  the 
leakage  is  small. 


Courtesy  of    Underwriters'  Laboratories,     Inc. 

Two  splices,  found  in  a  department  store,  made  by  the  "handy-man". 
Splices  improperly  made  are  extremely  hazardous  because  of  the  in- 
security of  contact,  the  wires  'will  heat  and  ignite  the  insulation,  over 
which  the  flame  will  travel. 

All  joints  should  be  well  made  and  soldered  as  an  un- 
soldered joint  is  liable  to  become  loosened  or  corroded,  in 
either  of  which  events  the  contact  between  the  wyires  would 
become  imperfect.  This  would  cause  heating  at  the  joint  and 
might  result  in  the  wTire  being  completely  melted  off  and  a 
dangerous  arc  being  formed  at  the  break.  A  good  mechanical 
joint  is  required  for  strength  should  the  soldering  give  way  or 
become  corroded  by  traces  of  acid  in  the  soldering  fluid  or 
flux  used. 


Courtesy  of  The   Insurance   Field. 

Outside  lines  well  supported  over  roofs. 

Where  outside  lines  are  supported  on  buildings,  they  must 
be  at  least  8  feet  above  the  highest  point  of  roofs  over  which 
they  pass  or  to  which  they  are  attached,  and  roof  structures 
must  be  substantial^  constructed  and  wherever  feasible,  wires 
crossing  buildings  should  be  supported  on  poles  independent 
of  the  building. 

This  is  intended  to  insure  that  under  no  conditions  could 
the  wires  sag  and  touch  the  roof ;  and  also  that  persons  walk- 
ing on  the  roofs  could  not  come  into  accidental  contact  with 
them.  Roof  structures  are  sometimes  found  which  are  too 
low  or  much  too  light  for  the  work,  or  which  have  been  care- 
lessly put  up.  A  standard  structure  which  is  to  hold  the  wires 
a  proper  distance  above  the  roof  in  all  kinds  of  weather  must 
not  only  be  of  sufficient  height,  but  must  be  substantially  con- 
structed of  strong  material. 

Where  outside  wires  are  brought  into  buildings,  special 
precaution  must  be  taken.  These  wires  are  known  as  service 
wires  or  services,  and  should  be  kept  free  from  contact  with 
anything  but  their  designed  supports.  Frequently  these  wires 


ISP^tPS^^^f 


Courtesy    of    Grouse-Hinds    Company. 

A  good  method  for  bringing  service  wires  underground  from  an 
overhead  line  to  the  cellar  of  a  building.  The  exposed  end  of  the  conduit 
has  a  terminal  fitting  which  prevents  water  flowing  into  the  conduit. 


53 

are  found  to  be  in  contact  with  the  building,  signs,  shutters 
and  awnings  offering  an  opportunity  for  a  fire,  through  the 
medium  of  an  arc.  That  portion  of  the  service  wire  from  the 
last  outside  support  into  the  building  must  have  rubber  in- 
sulation as  an  extra  precaution.  One  method  used  to  bring 
these  wires  into  a  building  is  to  have  them  enter  through 
bushed  holes,  with  the  porcelain  bushings  slanting  upward 
toward  the  inside,  the  service  to  have  "drip  loops"  also  that 
water  may  not  follow  the  wires  inside  the  building  and  es- 
tablish an  arc  around  the  service  cut-out  and  the  wet  wood. 


Service  wires  secured  to  side  of  building  by  petticoat  insulators  and 
entering  building  through  terminal  fitting  which  prevents  moisture  in 
conduit  through  brick  'wall. 

Another  method  is  to  install  the  several  wires  in  a  metal 
conduit,  this  conduit  extending  from  the  basement  where  the 
wires  enter,  up  the  side  of  the  building  well  out  of  the  reach 
of  persons.  On  the  upper  end  of  the  conduit  a  fitting  known 
as  a  "pipe  cap"  should  be  installed,  which  fitting  protects  the 
wires,  in  the  conduits,  from  moisture. 


54 

Where  lead  covered  cables  are  strung  overhead,  the  out- 
side sheath  should  be  permanently  and  effectively  grounded, 
as  any  breakdown  of  insulation  between  the  conductor  and  the 
sheath  makes  the  cable  practically  a  bare  live  wire,  the  danger- 
ous condition  of  which  is  obvious.  The  ground  connection 
required  by  this  section  keeps  the  sheath  at  the  potential  of 
the  earth  and  prevents  a  dangerous  flow  of  current  from  the 
sheath  at  any  other  point.  The  ground  wire  should  be  of 
sufficient  size  and  so  well  connected  to  the  sheath  and  to  the 
earth  that  it  can  safely  carry  the  current  necessary  to  melt 
the  fuses  protecting  the  cables. 


Weatherproof    and     Rubber- 
Covered  Wire  at  Service  Entrance. 

Details  of  service  wires  entering  building. 

Trolley  wires  must  be  of  ample  size  for  mechanical 
strength  and  are  usually  No.  O  B.  &  S.  gage  copper  or  No. 
4  B.  &  S.  gage  Silicon  Bronze.  Protection  against  crosses 
must  be  ample  and  street  railway  trolleys  and  feeder  cables 
must  be  capable  of  being  disconnected  at  the  powder  stations 
or  of  being  divided  into  sections  so  that,  in  case  of  fire  on  the 
railway  route,  the  current  may  be  cut-off  from  that  particular 
section  and  not  interfere  with  the  work  of  the  fire  department. 


ELECTROLYSIS. 

Electrolysis  is  the  chemical  decomposition  of  a  conduct- 
ing substance  caused  by  the  flow  of  current  through.  One 
specific  form  of  electrolysis  is  the  "eating  away"  or  corrosion 
of  underground  metallic  structures  due  to  the  passage  of 
stray  electric  currents  from  them.  The  other  important  form 


55 

of  electrolysis  is  the  decomposition  of  electrolytes  by  electric 
currents ;  electroplating  and  electrotyping  are  practical  ex- 
amples of  this.  If  a  current  passes  from  one  conductor  (posi- 
tive plate  or  anode,  Fig.  i,  I)  through  an  electrolyte  to  an- 
other conductor  (negative  plate  or  cathode),  the  electrolyte 
will  be  decomposed  and  the  anode  may,  under  certain  con- 
ditions, also  b'e  decomposed. 

Example. — If  a  current  be  forced  from  one  platinum 
electrode  to  another  through  a  copper  sulphate  electrolyte,  as 
shown  in  Fig.  I,  I,  metallic  copper  will  be  dissociated  from 
the  solution  and  deposited  on  the  cathode.  The  remaining 
components  of  the  copper  sulphate  will  unite  with  the  water 
in  the  "solution  to  form  sulphuric  acid.  This  illustrates  how 
an  electric  current  can  decompose  electrolytes.  This  principle 
can  be  readily  demonstrated  (Fig.  I,  II)  by  using  a  couple  of 
dry  cells  as  a  source  of  energy,  a  couple  of  iron  nails  as 
electrodes  and  a  solution  of  blue  vitriol  (copper  sulphate — 
a  crystal  the  size  of  a  walnut  in  a  tumbler  full  of  water)  for 
an  electrolyte  and  a  glass  tumbler  for  a  jar. 

Electrolytes  are  solutions  in  water  of  acids,  bases, 
(alkalies)  and  salts.  They  are  decomposed  when  an  electric 
current  passes  through  them.  The  exciting  solutions  in 
primary  and  secondary  cells  and  the  solutions  used  in  electro- 
plating and  electrotyping  are  examples  of  electrolytes. 

Electrolysis  of  underground  metallic  structures  is  illus- 
trated in  Fig.  2.  Direct  current  railway  systems  practically 
always  use  the  track  as  a  return  conductor.  The  return 
current  "leaks"  from  the  track,  which  is  always  in  contact 
with  the  earth,  and  often  seeks  a  route  of  minimum  resistance 
through  water  mains,  cable  sheaths  and  other  metallic  under- 
ground structures.  Where  these  leakage  currents  enter  the 
buried  metallic  systems  (A,  Fig.  2)  there  is  no  trouble.  But 
at  locations  (B)  where  the  stray  currents  leave,  electrolysis, 
wasting  away  of  the  metal,  occurs. 

The  action  is  similar  to  that  of  an  electroplating  process. 
The  water  main  in  the  illustration  B  is  the  anode.  The 
chemical  salts  in  the  earth  in  the  combination  with  the 
moisture  in  it  constitute  an  electrolyte.  The  ground  plate 
or  connection  at  the  generating  station  is  the  cathode.  With 
large  railway  systems  the  leakage  may  be  very  great,  in  which 
case  the  consequent  eating  awray  of  underground  metals  is 
extensive.  In  some  cases,  a  service  water  pipe  may  be  eaten 
entirely  through  in  a  month.  This,  you  will  at  once  recognize, 


I-  Principle 


E-  Experimental  Outfit 


Fig.  1  —  Illustrating   Electrolysis. 


...  -500-Volt  Direct-Current  Oenc'a'cr 


..-Trolley  Wire 


"•>,'.•".':        '"'*  '*     '-'.'^.  ...*-'".B//r.  V'  WatrrMa:n-'  Current-''  Rail-' 

"•=-.-.:•::::::.    ^-    ,'       ^Current       mt*  '  Lwvingtoil;  Return 

Earth-..'      ^rrr..;--.,, •;'..>-',.-•  /ftw/h^ 

/    ~  ""--T.^ "..--•'*"''  Water  Main 

Ground '  &t  St&fior: 

Fig.  2 — Illustrating  Cause  of  Electrolysis  of  a  Water  Main. 

Copper  Hanger  Wires  *^ 


''-Primary  Cel  13,  Source  of - 
Electric  Current 


Fig.  3— A  Silver   Electroplating   Outfit. 
Tract 


ft'A*. 


Courtesy   of  The   Insurance    Field. 

If  as  shown  in  the  above  diagram  the  tracks  of  a  street  railway,  a 
line  of  water  pipe  and  a  telephone  cable,  all  form  conducting  paths  toward 
the  power  house,  the  current  on  the  tracks  will  divide  itself  up  and  the 
greater  part  stay  on  the  tracks,  but  part  of  it  taking  the  pipe  and  part 
the  telephone  cable. 


57 

bears  a  very  close  and  a  very  vital  relationship  to  the  public 
fire  protection  systems.  The  most  effective  method  of  cor- 
recting such  electrolytic  action  is  to  minimize  the  tendency 
for  its  occurrence.  Just  how  this  may  best  be  accomplished 
all  engineers  have  not  agreed,  although  a  number  of  plans 
have  been  tried.  One  method  has  been  that  of  providing  a 
low  resistance  path  back  to  the  generating  station  by  connect- 
ing the  station  ground  directly  with  the  rails  at  various 
locations  with  heavy  copper  return  conductors  and  bonding 
the  rails.  The  double  overhead  trolley  has  been  tried  and, 
while  this  did  solve  the  problem,  in  so  far  as  electrolysis  was 
involved,  it  introduced  several  other  difficulties.  The  United 
States  Bureau  of  Standards  is  recommending  a  system  of 
transpositions,  or  reversals,  and  this  method  is  being  installed 
in  the  city  of  Springfield,  Massachusetts.  This  method,  I 
believe,  had  its  origin  in  Germany,  but  most  of  us  are  not 
concerned,  at  this  time,  in  anything  that  had  its  origin  in 
Germany. 

Whenever  a  current  passes  through  a  solution  of  a  salt 
of  a  metal,  the  metal  will  be  extracted  electrically  from  the 
solution  and  deposited  on  the  negative  plate  or  cathode.  Fig. 
i  illustrates  a  sort  of  electroplating  process.  Electroplating 
consists  in  coating  by  electrolysis  a  baser  metal  with  copper, 
gold,  silver,  nickel  or  almost  any  other  metal. 

Example. — Fig.  3  shows  a  silver  plating  outfit.  In  modern 
commercial  outfits  low-voltage,  direct-current  generators  are 
practically  always  used  as  sources  of  current  instead  of 
primary  cells.  The  process  is  about  as  follows :  The  surface 
of  the  object  to  be  plated  is  thoroughly  cleaned  of  all  fatty 
matter.  The  object  is  connected  to  the  negative  pole  of  the 
source  of  electrical  energy  and  thus  constitutes  a  cathode. 
The  electrolyte  is  a  solution  of  some  chemical  salt  of  the 
metal  to  be  deposited.  For  silver,  cyanide  of  silver  is  used ; 
for  copper,  copper  sulphate,  etc.  To  maintain  the  strength 
of  the  solution,  a  piece  or  anode  of  the  metals  to  be  deposited 
is  attached  to  the  positive  pole  of  the  electro-motive-force 
source.  (Note: — Electro-Motive-Force  is  generally  expressed 
as  E.  M.  F.)  The  current  in  flowing  through  the  solution  de- 
posits the  metal  of  the  solution  on  the  cathode.  Certain 
metals  such  as  iron,  steel,  zinc  and  lead  cannot  be  plated  with 
certain  other  metals,  such  as  gold,  silver  and  nickel,  until1 
after  they  have  first  been  given  a  thin  plating  of  copper. 

Electrotyping  is  an  electrolytic  process,  similar  to  electro- 
plating, whereby  wood  cuts,  type  and  like  objects  can  be 


58 

reproduced  in  metal,  usually  copper.  An  impression  of  the 
object  to  be  reproduced  is  taken  in  warm  plaster  of  paris  or 
similar  molding  material.  The  surface  of  the  mold  thus 
made  is  thinly  coated  with  some  fine  metallic  substance,  such 
as  powdered  graphite,  to  render  it  conducting.  The  mold  is 
then  immersed  in  a  copper  sulphate  solution  bath  and  its 
conducting  surface  is  so  connected  to  the  negative  pole  of  a 
source  of  electric  current  that  it  constitutes  a  cathode.  It  is 
then  treated  much  like  any  other  object  to  be  plated.  When 
the  copper  coating  on  it  has  become  about  the  thickness  of  a 
visiting  card,  it  is  removed  and  reinforced  by  pouring  molten 
metal  on  its  back.  If  it  is  to  be  used  for  printing  it  is  backed 
so  as  to  be  the  same  height  as  type. 

In  the  electrolytic  refining  of  metals  the  process  is  some- 
what similar  to  electroplating  (Fig.  3).  The  impure  metal 
to  be  refined  is  suspended  as  an  anode  in  a  solution  of  its 
salts.  Current  is  forced  through  the  solution  from  the  anodes 
to  the  cathodes.  Pure  metal  only  is  deposited  on  the  cathode. 
The  impurities  of  the  anodes  fall  to  the  bottom  of  the  tank 
as  the  pure  metal  is  extracted  from  them.  The  electrolytic 
refining  of  copper  is  a  very  important  process  commercially. 

HIGH  TENSION  LINES. 

A  reference  has  been  made  to  high  tension  lines,  more 
especially  to  the  overhead  lines  of  this  class  which,  unless 
properly  arranged,  may  increase  the  fire  loss. 

"Accidental  crosses  between  such  lines  and  low- 
potential  lines  may  allow  the  high-voltage  current  to 
enter  buildings  over  a  large  section  of  adjoining 
country.  Moreover,  such  high-voltage  lines,  if  car- 
ried close  to  buildings,  hamper  the  work  of  firemen 
in  case  of  fire  in  the  building.  The  object  of  the  rules 
is  to  so  direct  this  class  of  construction  that  no  in- 
crease in  fire  hazard  will  result,  while  at  the  same 
time,  care  has  been  taken  to  avoid  restrictions  which 
would  unreasonably  impede  progress  in  electrical 
development." 

The  very  best  way  to  guard  against  accidental  contact 
and  crosses  between  the  high-tension  lines  and  other  circuits 
is  to  have  them  follow  different  routes.  This,  however,  is  not 
always  possible,  but  it  has  been  accomplished  by  mutual 
agreement  of  the  parties  interested  even  when  a  change  in 


59 


Courtesy   of  Commissioner  James   E.   Cole,   Wire   Department,   Boston,   Mass. 

Collection  of  salts  on  wire  in  a  damp  basement,  illustrating  a  form 
of  electrolysis. 


6o 

one  of  the  routes  will  be  necessitated.  When,  however,  these 
lines  do  cross  each  other,  special  precautions  must  be  taken 
to  prevent  contact  between  the  two  lines  especially  should 
one  of  them*  break.  The  rules  contain  detailed  specifications 
for  the  safe  construction  of  crossovers  and  other  details  of 
high-voltage  lines. 

TRANSFORMERS. 

Transformers  should  preferably  be  kept  outside  of  build- 
ings. In  general,  it  is  dangerous  to  locate  transformers  with 
oil-filled  cases  inside,  as  it  is  entirely  possible  for  a  breakdown 
of  insulation  to  ignite  the  oil,  which  may  result  in  a  very 
stubborn  fire.  For  the  same  reason,  the  placing  of  trans- 
formers on  roofs  is  also  objectionable.  Sometimes  we  face 
conditions  which  make  it  necessary  to  install  these  trans- 


Courtesy  of  The  Insurance  Field. 

Method  of  installing  an  oil  insulated  transformer  iri^a  vault  of  fire- 
proof construction.  Transformer,  however,  should  never  be  installed  in 
a  building  unless  in  a  fireproof  vault  as  shown  above. 


6i 

formers  within  buildings.  When  this  is  done,  the  trans- 
formers must  be  installed  in  a  fire-proof  vault,  having  a 
standard  fire  door,  with  a  raised  sill  across  the  doorway  to 
prevent  burning  oil  from  flowing  into  the  building.  These 
vaults  should  be  well  ventilated  to  the  outside  air  and,  if 
possible,  should  be  drained  that  the  burning  oil  may  flow  from 
the  vault  without  doing  further  damage. 

GROUNDING  OF 
SECONDARY  CURRENTS. 

The  grounding  of  secondary  currents  is  for  the  purpose 
of  providing  protection  to  human  life  from  electric  shock. 
The  grounding  of  the  secondary  leads  to  a  harmless  point  all 
stray  currents  from  any  source  which  may  become  crossed 
with  the  secondary  service. 

As  early  as  1900  this  practice  was  found  to  be  beneficial 
by  actual  experiment  and  test,  and  in  1905  the  subject  was 
discussed  in  meetings  of  the  national  electrical  engineering 
societies.  From  that  date  the  practice  of  grounding  second- 
aries became  more  or  less  general ;  beginning  with  1907  var- 
ious engineering  organizations  recommended  the  practice  as 
desirable,  and  in  1915  such  organizations  as  the  American 
Institute  of  Electrical  Engineers,  the  National  Electric  Light 
Association,  and  the  National  Board  of  Fire  Underwriters 
recommended  that  the  practice  be  made  mandatory. 

The  secondary  voltage  value  should  determine  the  ques- 
tion of  when  to  ground  the  service,  and  it  is  now  standard 
practice  to  ground  all  secondary  service  in  the  lowrer  voltage 
group,  up  to  and  including  150  volts. 

There  are  three  points  at  which  a  secondary  system  may 
be  grounded,  namely, 

At  the  generating  station, 

At  the  transformer, 

On  the  customer's  premises. 

If  the  generating-station  grounding  point  is  used,  it  is 
necessary  to  have  the  overhead  grounded  wire  running  over 
all  the  lines  carrying  the  secondary  system,  which  subjects 
linemen  and  overhead  workers  on  pole  lines  to  an  unnecessary 
hazard,  brought  about  by  the  presence  of  this  grounded  wire 
within  the  zone  of  their  operations  on  the  pole.  This  practice, 
from  an  operating  standpoint  is  considered  undesirable.  More- 


62 

over  the  breaking  or  disconnection  of  this  wire  removes  all 
protection. 

If  the  second,  or  pole-transformer,  point  for  grounding  is 
used,  the  overhead  system  is  relieved  of  the  hazard  just  de- 
scribed and  the  secondary  service  receives  considerable  pro- 
tection, as  theoretically  any  stray  current  getting  onto  the 
circuits  will  be  led  to  the  ground  through  the  grounding  wire 
run  from  the  transformer  on  the  pole  to  the  ground  at  that 
point,  but  this  method  does  not  give  the  greatest  protection 
to  the  user  of  electrical  energy. 

The  third  and  only  complete  method  from  the  protection 
standpoint  is  to  ground  within  the  customer's  premises,  so 
that  the  location  of  the  point  of  protection  will  be  as  near  as 
possible  to  the  person  subject  to  the  electrical  hazard,  thus 
protecting  the  user  from  the  stray  currents  occasioned  by  the 
crossing  of  wires  from  any  cause,  even  though  such  cross 
occurs  immediately  outside  of  the  building  served.  Such 
grounds  are  free  from  disturbance  from  any  outside  cause. 

It  has  been  clearly  demonstrated  that  an  unreliable 
ground  is  most  undesirable  from  a  protection  standpoint  and 
that  a  ground  of  minimum  resistance  and  maximum  perma- 
nency gives  the  most  complete  protection.  Therefore,  the 
practice  of  grounding  to  active  underground  water-piping 
systems  affords  the  most  perfect  ground  connection  and  by 
placing  such  connection  immediately  within  the  walls  of  a 
building  served  ahead  of  any  wrater  meters  or  accessories  a 
protective  connection  is  secured  at  the  point  nearest  to  the 
user  of  the  electrical  energy  and  at  a  point  which  can  best  be 
guarded  for  permanency  of  the  connection. 

Several  years'  experience  throughout  the  United  States 
with  thousands  of  cases  of  connections  as  just  described 
proves  conclusively  that  a  connection  of  this  nature  is  in  no 
way  harmful  to  the  water-piping  systems.  It  is  fortunate  that 
this  fact  is  recognized  by  nearly  all  of  the  water-distributing 
companies  throughout  the  country,  because  the  continuity 
of  a  good  ground  connection  is  essential  for  continued  pro- 
tection, and  the  locating  of  the  protective  connection  just 
within  the  walls  of  a  building,  as  described,  makes  the  guard- 
ing and  inspection  of  such  work  easy  of  accomplishment. 
This,  combined  with  the  desirability  of  having  the  ground 
connection  as  near  as  possible  to  the  user  of  the  current, 
makes  this  point  of  grounding  the  most  logical  for  good  re- 


63 

suits.     This  is  a  standard  method  and  is  fast  becoming  the 
general  practice  in  this  country. 

The  ground  wire  should  be  a  continuous  wire  without 
joints,  and  of  sufficient  length  to  be  connected  to  the  service 
side  of  the  main  line  fuses.  The  ground  wire  should  be  at 
least  as  large  as  the  largest  wire  used  for  service  mains 
(except  that  a  wire  larger  than  No.  oooo  is  not  necessary),  but 
in  no  case  should  it  be  less  than  No.  6  B.  &  S.  gage.  When 
a  building  is  wired  in  metal  conduit,  armored  cable  or  metal 
raceways,  the  ground  wire  for  such  metal  installations  must 
never  be  connected  to  the  ground  wire  of  the  secondary 
circuit. 


Part  No.  4. 

INSIDE  WORK. 

In  a  former  lecture,  the  intimate  relationship  of  electricity 
to  our  industrial  life  was  shown  through  its  application  in  the 
form  of  power  by  means  of  the  motor.  The  rules  which  we 
will  consider  this  evening,  are  for  a  more  intimate  relation- 
ship, even  into  our  home  life,  as  well.  We  must  never  lose 
sight  of  this  fact,  electricity  used  with  discretion  is  the  safest 
form  of  energy  and  the  rules  are  for  the  purpose  of  maintain- 
ing this  confidence.  We  should  always  bear  in  mind  that 
householders  are  not  electrically  trained,  and  their  attention 
is  distracted  from  the  electrical  features  by  the  other  activities 
and  processes  occurring  about  them.  To  the  householder,  of 
course,  electrical  features  of  his  household  are  mere  incidents. 
For  this  class  of  user  of  electricity,  the  greatest  amount  of 
safeguarding,  physical  and  educational,  must  be  thrown  about 
the  electrical  wiring  and  equipment. 

This  class  of  rules,  however,  does  not  apply  to  household 
installations  and  equipments  alone,  but  contains  all  of  the 
rules  for  wiring  for  light,  heat  and  power  as  contained  within 
buildings.  They  do  not  include  the  rules  for  Signaling  Sys- 
tems, such  as  telephone,  telegraph,  fire  and  police  alarms,  and 
similar  equipments,  as  these  circuits  do  not  present  hazards 
in  themselves,  being  hazardous  only  from  being  crossed  with 
light,  heat  and  power  wires,  or  on  account  of  lightning  dis- 
charges. 

The  present  methods  for  wiring  inside  of  buildings  are 
the  result  of  experience  extending  over  the  period  between 


64 

the  earliest  applications  of  electricity  to  the  present  time. 
Methods  have  changed  as  the  possible  dangers  were  recog- 
nized, and  as  improved  means  of  guarding  against  them  were 
devised.  The  net  result  of  this  experience  has  been  on  the 
one  hand  an  elaboration  of  rules  and  an  approach  to  a  few 
standard  systems  of  construction,  and  on  the  other  hand  the 
production  of  an  almost  endless  variety  of  materials  available 
for  electrical  purposes. 

The  earlier  installations  were  laid  on  timbers  under  floors, 
in  partitions  and  over  walls  without  supports,  in  channels  cut 
for  them  in  wood  casings  or  supported  by  wood  cleats  without 
regard  to  protecting  the  wires  from  injury  or  the  adjacent 
combustible  materials  from  being  ignited  by  overheated  wires, 
or  by  arcs.  It  was  the  very  best  type  of  installation  possible 
at  that  time.  These  crude  methods,  however,  have  been  most 
wholly  abandoned  and  it  is  generally  conceded  that  the  best 
protection  against  electrical  fires  lies  in  the  adoption  of  the 
most  approved  methods  even  when  the  first  cost  of  an  installa- 
tion is  increased  to  some  extent. 

In  buildings  of  the  better  and  larger  class,  such  as  our 
large  office  buildings,  our  present  day  apartment  houses, 
factories,  churches  and  theatres,  the  electrical  installations  re- 
ceive the  same  degree  of  careful  study  and  planning  as  does 
the  general  planning  of  the  building  and  plans  are  frequently 
made  by  electrical  engineers  acting  under  the  instructions 
from  the  architect.  The  possible  efficiency  of  the  installation 
is  most  carefully  considered,  the  extent  of  the  equipment,  the 
amount  of  electrical  energy  necessary,  the  method  of  distri- 
bution and  the  installation  of  the  wires  are  very  completely 
arranged,  that  the  greatest  efficiency  and  economy  may  be 
gained.  This  economy  must  not  be  entirely  confounded  with 
the  first  cost;  it  applies  to  the  operation  of  the  completed 
installation.  With  the  smaller  installations,  we  have  our 
greatest  difficulty,  inasmuch  as  we  do  not  have  this  careful 
planning  and  supervision,  and  the  wiring  oftentimes  is  an 
afterthought.  Frequently  the  work  is  given  to  the  lowest 
bidder,  without  regard  to  his  understanding  of  the  problems 
involved  or  his  method  of  solving  them,  and  naturally  we 
have  cheap  construction.  However,  the  general  tendency  is 
for  an  improvement  of  all  electrical  installations,  and  with  the 
supervision  which  is  being  given  by  municipalities  and  by  the 
underwriters,  as  a  whole,  our  installations  are  remarkably 


65 

safe,  and  the  comparatively  few  fires  at  the  present  time  are 
caused  by  defective  electrical  installations. 


SERVICES. 


The  method  of  bringing  service  wires  into  a  building  re- 
quires care  and  attention.  We  have  explained  the  two 
methods  which  are  most  generally  used.  One,  you  will  recall, 
was  where  each  wire  entered  the  building  through  separately 
bushed  holes,  and  the  other  was  where  the  low-potential  wires 
entered  through  a  metal  conduit,  which  usually  extends  into 
the  basement.  Rarely  do  we  find  high  tension  wires  entering 
buildings,  and  when  they  do,  special  rules  which  provide  for 
multiple  conductor,  lead  sheathed  cable,  installed  in  unlined 
metal  conduits  with  the  view  of  protecting  the  conductors 
against  moisture,  are  followed. 

At  the  nearest  readily  accessible  place  to  where  the  ser- 
vice wires  enter  the  building,  must  be  installed  the  protection 
of  the  system  in  the  form  of  service  fuses  and  service  switch. 
This  switch  is  usually  of  the  knife  blade  type  and  must  be  so 
installed  that  all  of  the  wiring  within  the  building  may  be 
entirely  disconnected  from  the  outside  wires.  The  service 
fuses  must  be  placed  between  the  service  switch  and  the  out- 
side wires  unless  the  switch  is  installed  in  a  metal  box  or 
cabinet. 

The  purpose  of  the  service  fuses  is  to  protect  all  of  the 
wiring  inside  the  building  from  overloads,  and  should  never 


66 


Courtesy    of  Metropolitan     Engineering    Company. 

The  three  preceding  pictures  illustrate  installation  of  meters,  plug 
and  open  link  fuses  and  wires  in  apartment  houses.  These  installations 
had  a  number  of  hazardous  conditions  and  were  typical  of  the  conditions 
of  electrical  installations  prior  to  the  adoption  of  the  National  Electrical 
Code. 


67 

be  installed,  unless  in  a  dust-tight  cabinet,  where  there  are 
flyings  of  inflammable  materials  or  so  that  the  molten  metal 
of  the  ''blowing"  fuse  will  ignite  combustible  and  inflammable 
material. 

Service  fuses  and  switches  are  in  several  forms,  from  a 
pair  of  small  "plug"  fuses  and  "knife"  switch  mounted  on  a 
porcelain  or  slate  base  to  those  of  large  capacity  mounted  ""on 
slate  or  marble  switchboard  placed  in  a  room  specially  ^de- 
ned  for  the  purpose,  to  which  the  lighting  and  power  mains 
are  connected  with  separate  fuses  and  switches  to  control  and 
protect  the  power  and  lighting  circuits. 

UNDERGROUND 
CONDUCTORS. 

It  is  practically  necessary  for  underground  conductors  to 
enter  a  building  through  the  foundation  wall,  in  the  basement. 
Where  underground  service  enters  building  through  tubes, 
the  tubes  must  be  tightly  closed  atf'outlets  with  asphaltum  or 
other  non-conducting  material  to  prevent  gases  from  entering 
the  building  through  such  channels.  It  is  not  desirable  to 
have  more  than  one  underground  service  from  a  subway  to 
supply  more  than  one  building,  as  it  is  not  advisable  to  have 
several  buildings  fed  through  one  building  thus  making  it 
necessary  to  enter  the  building  having  the  general  service  in 
order  to  cut-off  the  current  in  another  building. 

GENERAL  RULES- 
ALL  VOLTAGES. 

No  wdre  smaller  than  No.  14  B.  &  S.  gage  is  permitted, 
except  for  fixtures  and  flexible  cord.  This  limitation  is  not 
because  of  the  carrying  capacity  of  the  wire,  but  it  has  been 
found  that  wires  smaller  than  No.  14  are  not  mechanically 
strong  enough  to  be  safely  used. 

SPLICES. 

We  have  had  your  attention  drawn  to  the  need  of  having 
our  joints  and  splices  properly  made.  While  this  may  seem 
to  be  elementary,  it  is  very  important.  A  poorly  made  splice 
offers  a  resistance  to  the  flow  of  current,  which  resistance  will 
heat  the  wire  and  the  heated  wire  will  then  inflame  the  insula- 
tion. For  general  wiring,  the  underwriters  have  never  found 


68 


Courtesy    Metropolitan    Engineering    Company. 

Installation  of  cut-out  and   switches  in 
the  cellar  of  a  large  apartment  house. 


individual  metal   cabinets   in 


69 

the  equivalent  for  good  soldered  joints  when  all  the  possible 
effects  of  corrosion,  alternate  heating-  and  cooling,  vibration, 
and  mechanical  strains  are  considered.  After  soldering,  wire 
joints  or  splices  must  be  covered  with  an  insulation  equal  to 
that  at  other  places  on  the  conductors.  This  is  usually  done 
by  winding  the  splices  or  joints  with  a  good  rubber  tape  over 
which  is  wound  a  "friction  tape"  of  fabric  impregnated  with 
compound. 

WIRES. 

Rubber  insulated  wire  must  be  used  for  all  concealed  work 
and  when  installed  in  damp  places  or  in  metal  raceways,  such 
as  conduits,  thin  wall  conduits  and  armored  cables.  For 
"open  work"  in  dry  places  where  the  voltage  is  not  over  550, 
slow-burning  insulation  may  be  used,  as  it  fulfills  every  re- 
quirement for  such  work,  is  less  expensive  and  will  not  carry 
fire. 


A  good  installation  of  open  'wiring;  the  wires  being  well  supported 
by  cleats  and  knobs  against  contact  with  building  and  pipes.  Wires  are 
also  protected  against  contact  with  each  other  through  means  of  porcelain 
cross-over  tubes,  which  tubes  are  prevented  from  sliding  along  the  wires 
by  cleats  secured  at  each  end. 

When  not  installed  in  conduits  or  other  metal  raceways, 
the  wires  must  always  be  separated  from  contact  with  walls, 
floors,  timbers,  and  partitions  by  non-combustible,  non- 


absorptive,  insulating  bushings,  such  as  glass  or  porcelain, 
and  must  be  kept  free  from  all  contact  with  pipes  or  any 
conducting  material.  This  requirement  is  without  regard  to 
the  type  or  extent  of  the  insulation  on  the  wires,  the  purpose 
being  that  the  insulation  of  the  conductors  from  each  other 
and  from  other  conducting  materials  must  be  sufficient  to 
furnish  the  necessary  protection  in  case  the  insulation  on  the 
wires  is  defective  or  becomes  injured  in  any  way. 

In  damp  or  wet  places,  the  relative  arrangement  of  the 
pipes  and  wires  should  be  such  that  the  wires  cannot  touch 
the  pipes  and  so  that  water  cannot  drop  from  the  pipes  on 
the  wires.  On  this  account  it  is  recommended  that  wires  be 
above  rather  than  below  the  pipes. 


Two  methods  for  protecting  wires  on  side  wall  against  mechanical  injury. 

CARRYING  CAPACITY. 

The  Code  prescribes  the  maximum  current  which  shall 
be  carried  on  copper  conductors  of  the  different  sizes.  These 
are  arranged  in  table  form  and  are  the  result  of  long  study 
and  many  careful  experiments.  A  reference  to  this  table, 
which  in  Rule  18,  of  the  Code,  will  show  that  Table  A,  which 
applies  to  wires  having  rubber  insulation,  is  lower  than  Table 
B,  which  is  for  wires  having  insulation  other  than  rubber. 
This  difference  is  because  the  rubber  insulation  will  deter- 


iorate  under  high  temperature.  These  tables,  please  remem- 
ber, are  to  be  used  for  inside  work  only.  It  has  been  stated 
that  for  any  given  size  of  wire,  a  current  about  three  times 
as  great  as  that  given  in  Rule  18,  will  cause  all  ordinary  in- 
sulations to  smoke,  this  being  the  margin  of  safety  provided, 
and  is  none  too  large  considering  that  often  wires  must  be 
installed  in  places  having  fairly  high  temperatures,  such  as 
boiler  rooms,  bake  houses,  drying  rooms  and  lumber  kilns. 
This  table  of  carrying  capacity  of  wires  is  sometimes  confused 
with  the  question  of  drop,  some  installing  wiremen  thinking 
that  if  they  use  a  wrire  large  enough  so  as  to  keep  inside  of 
the  allowable  capacity,  as  stated  in  the  table,  it  wrill  be  ample, 
regardless  of  the  distance  the  circuit  is  run. 


Courtesy  Underwriters'  Laboratories,  Inc. 

Fire  caused  between  the  ceiling  and  floor  by  an  arc  between  the  wires 
for  the  electric  light  and  a  gas  pipe. 


DROP. 

Since  it  requires  power  to  keep  a  current  flowing,  there 
must  be  some  power  used  in  keeping  the  current  flowing- 
through  the  line  wires  of  any  system.  Of  course,  all  power 
used  in  this  way  is  wasted  and  is  therefore,  called  Line  Loss 
or  Drop.  As  an  example,  let  us  consider  a  dynamo  supplying 
current  to  a  motor,  500  feet  away  from  the  dynamo,  and  we 


72 

will  suppose  the  motor  requires  50  amperes  of  current  at  a 
pressure  of  220  volts.  From  Table  A,  Rule  18,  we  find  that 
No.  6  wire  could  be  used.  But,  as  I  have  stated,  some  power 
is  lost  in  driving  the  current  of  50  amperes  through  the  1,000 
feet  of  line  wire  and,  if  the  wire  is  small,  its  resistance  will  be 
large  and  so  more  power  will  be  lost  on  the  line  wires.  So 
you  can  see  that  the  part  of  the  dynamo  voltage  required  to 
drive  the  working  current  over  the  supply  wires  is  called 
"drop".  Suppose,  in  an  installation  similar  to  the  one  I  have 
endeavored  to  make  clear,  it  is  specified  that  the  drop  shall 
not  be  over  I  per  cent,  of  the  total  voltage.  One  per  cent,  of 


Courtesy    of    General    Electric    Company. 

AN  OIL  SWITCH. 

For  high-tension  work  oil  switches  are  used  almost  exclusively,  and 
in  low-tension  'work  they  are  also  extensively  used  on  account  of  the 
compactness  of  construction  and  the  reliability  of  the  operation.  The 
arc  being  completely  enclosed,  this  switch  can  be  used  in  places  where 
there  is  dust  or  gas.  The  characteristic  features  of  this  type  of  switch 
are:  knife  blade  contacts  submerged  in  oil;  live  parts  carried  on  porcelain 
base  affording  a  permanent  insulation  between  adjacent  poles,  and  between 
the  frame  and  live  parts;  compactness  and  accessibility;  enclosure  of  all 
live  metal  parts.  Each  contact  jaw  has  attached  to  it  an  arcing  piece 
which  takes  the  final  break,  thus  preventing  any  burning  of  the  jaws. 
The  contact  making  parts  are  enclosed  in  a  sheet  metal  oil  tank  which 
has  an  insulating  lining.  The  above  pictures  show  the  oil  tank  assembled 
and  separated  from  its  supports. 


73 

220  volts  is  2.2  volts.  The  current  in  the  line  equals  the 
voltage  to  force  the  current  over  the  line  divided  by  the  ohms 
resistance  of  the  line. 

2.2 

In  this  case,  50  =  -  - ,   or   the   resistance   of   the 

resistance 

2.2 
1,000  feet  of  wire  must  not  be  more  than  -      -  ohms  or  .044 

50 

ohms.  From  the  wire  table  of  resistance  as  prepared  by  the 
U.  S.  Bureau  of  Standards  and  the  American  Institute  of 
Electrical  Engineers,  we  find  that  a  No.  oooo  wire  will  be 
required.  Thus  the  necessity  of  keeping  the  loss  of  power 
low  on  the  line  may  necessitate  the  use  of  a  larger  wire  than 
would  be  needed  for  safety  under  the  rules.  There  are  cases, 
of  course,  where  the  distance  between  the  dynamo  and  the 
load  is  short  and  where  a  smaller  wire  than  that  required 
on  account  of  the  heating  effect  might  be  used  and  keep  the 
"drop"  within  reasonable  limits. 

SWITCHES,  CUT-OUTS  AND 
CIRCUIT  BREAKERS. 

Even  in  the  earliest  stages  of  electric  wiring,  it  was  evi- 
dent that  some  means  must  be  provided  for  protecting  electric 
conductors,  appliances,  and  machinery  from  excessive  currents 
and  overloads.  For  this  purpose,  short  lengths  of  metal  con- 
ductors having  a  low  fusing  point  were  placed  in  circuit  with 
the  conductor,  and  were  so  designed  that  a  slight  increase  in 
current  above  the  normal  amount  would  melt  the  fuse  and 
open  the  circuit.  The  practice,  to-day,  is  to  use  fuses  of  the 
plug  and  cartridge  type,  and,  under  some  conditions,  the  open 
link  fuse,  which  corresponds  to  the  earliest  form  of  fuse. 
Circuit-breakers,  which  are  automatic  in  their  operation,  are 
used,  instead  of  fuses  in  installations  of  the  larger  size.  A 
fuse  and  a  circuit  breaker  differ  somewhat,  in  that  a  fuse  is 
an  element  designed  to  melt  or  dissipate  at  a  predetermined 
value  and  is  destroyed  when  its  intended  function  has  been 
performed.  A  circuit  breaker  is  designed  to  open  a  current- 
carrying  circuit,  the  same  as  a  fuse,  but  without  injury  to 
itself.  A  circuit  breaker  may  be  automatic  or  manually  oper- 
ated. 


74 


Courtesy    of    General    Electric    Company. 


EXPULSION  FUSES. 

The  above  pictures  represent  an  expulsion  fuse  in  and  out  of  circuit. 
In  this  device  there  is  a  short  fuse  wire  mounted  between  two  terminals, 
one  of  which  is  attached  to  the  end  of  a  long  lever.  When  the  fuse  is 
blown  this  terminal  is  released  and  a  spring  acts  upon  the  lever  to  in- 
crease the  gap  between  the  terminals  to  the  necessary  length  to  put  out 
the  arc. 


It  is  quite  necessary  that  switches  and  cut-outs  should 
never  be  installed  in  the  vicinity  of  easily  ignitable  material 
or  where  exposed  to  inflammable  gases  or  dust  of  any  charac- 
ter, or  to  the  flyings  of  any  combustible  materials,  such  as 
would  be  found  in  cotton  mills,  wood  working  plants,  flour 
mills,  grain  elevators,  gas  houses,  starch  making  plants, 
bakeries,  etc.  In  the  case  of  switches,  especially  of  the  knife- 
blade  type,  when  the  switch  is  thrown,  there  is  more  or  less 
of  an  arc,  which  will  ignite  flyings  of  combustible  materials 
or  gases.  While  our  present  day  enclosed  fuses  should  blow 
without  a  flash,  it  is  not  considered  safe  to  permit  them  in 
these  locations,  owing  to  the  possibility  of  the  fuse  "going 
bad",  as  it  were,  when  it  is  called  upon  to  operate  through  an 
overload  on  the  system  which  it  protects. 


75 


Courtesy    of    General    Electric    Comj 


A  power  installation  in  which  the  starting  device,  which  is  a  compen- 
sator, is  protected  by  automatic  circuit  breakers  designed  for  use  on 
alternating  current.  The  above  is  a  good  type  of  installation,  all  of  the 
wires  being  in  conduit  and  there  being  no  exposed  current  carrying  parts. 

CONSTANT  CURRENT 
SYSTEMS. 

These  systems  are  but  little  used  in  buildings  to-day,  the 
high-efficiency  lamps  having  almost  entirely  replaced  them. 
They  are  in  general  use,  however,  for  the  lighting  of  our 
streets.  The  potential  of  these  circuits  range  from  2,200  volts 
to  4,000  volts,  and  it  is,  therefore,  necessary  for  such  wires  to 


Courtesy   of   Trumbull   Electric   Manufacturing   Company. 

A  two-pole   knife    switch,   which    should    always   be   mounted   on    a 
slate  base. 


76 

be  well  insulated.  The  present  make  of  arc  lamps  are  en- 
closed, and  therefore  there  is  little  danger  from  sparks  of  hot 
carbon  falling  from  the  lamps,  as  was  the  case  a  number  of 
years  ago,  when  this  method  of  lighting  was  so  generally 
used,  the  lamps  at  that  time  being  of  the  open  or  unprotected 
type. 


Courtesy  of  Trumbull  Electric  Manufacturing   Company. 

Steel  cabinet  for  the  installation  of  cut-outs. 

CONSTANT  POTENTIAL 
SYSTEMS. 

In  the  Rules  we  will  find  the  Constant  Potential  Systems 
to  have  been  divided  into  three  classes,  known  as  low  potential 
systems,  which  are  of  550  volts  or  less ;  high  potential  systems, 
which  are  between  550  volts  and  3,500  volts ;  and  extra  high 
potential  systems,  which  are  above  3,500  volts. 

The  most  common  in  use  for  lighting  and  power  are  no 
volt  two-wire  systems,  220  volt  three-wire  systems,  there 
being  no  volts  between  the  neutral  and  either  of  the  outside 
wires.  These  two  systems  are  used  on  both  direct  current  and 
alternating  current,  although  alternating  current  has  very 
largely  replaced  the  direct  current  systems.  The  street  rail- 
ways use  a  direct  current  system,  with  a  ground  return,  which 


Courtesy  of  Trumbull   Electric  Manufacturing   Company. 

A  combination  three-pole  plug,  double  branch  cut-out  and  knife 
switches.  Cut-outs  of  this  type  are  intended  to  be  used  for  voltages  not 
greater  than  125. 


77 

systems  range  from  500  volts  to  600  volts.  Most  of  our  power 
circuits  are  for  220  and  550  volts  alternating  current  systems, 
although  the  use  of  2,300  volt  alternating  current  motors  is 
being  increased,  whereas  but  a  few  years  ago  they  were  but 
frequently  seen. 


Courtesy  of  Trumbull  Electric  Manufacturing   Company. 

A  combination  two-pole  cut-out  and  switches,  double  branch,  for  use 
•with  voltages  not  greater  than  125. 


AUTOMATIC  CUT-OUTS. 

These  are  the  devices  which  are  intended  to  protect  the 
circuits  and  appliances  throughout  the  installation  from 
overloads,  and  where  practicable,  should  be  grouped  so  as  to 


Courtesy  of  Trumbull  Electric  Manufacturing  Company. 

Two  and  three  wire   single  branch  combination  cut-out  and   switch, 
intended  for  use  on  voltages  not  greater  than  125. 

make  their  inspection  and  maintenance  easier,  and  also  on 
account  of  usually  being  able  to  find  a  safer  location  than 
when  they  are  scattered  over  a  building.  It  is  also  better  to 
install  the  cut-outs  in  cabinets,  so  that  a  "blowing  fuse"  can 
cause  no  trouble,  other  than  disconnecting  the  circuit. 

For  general  wiring,  the  rules  require  that  no  set  of  small 
motors,  small  heating  devices  or  incandescent  lamps,  nor  more 
than  16  medium  size  or  25  candelabra  size  sockets  or  lamp 
receptacles  requiring  more  660  watts,  shall  ultimately  be 
dependent  upon  one  cut-out.  The  purpose  of  this  rule  is  to 
secure  such  a  subdivision  of  the  fuses  that  no  very  large  cur- 
rents can  flow  for  any  long  time  over  any  part  of  the  small 
wiring  without  opening  a  fuse  and  thus  the  effects  of  a  short- 
circuit,  or  other  accident  will  be  very  much  minimized. 


Courtesy    of    General    Electric    Company. 

AUTOMATIC  CIRCUIT  BREAKER. 

The  above  is  a  circuit  breaker  intended  to  be  used  on  a  Direct  Current 
circuit.  It  is  a  device  which  automatically  opens  the  circuit,  without  injury 
to  itself,  in  event  of  abnormal  conditions  in  the  circuit.  In  circuits  of 
large  capacity  a  circuit  breaker  is  more  desirable  than  large  fuses  because 
of  the  expense  in  replacing  the  latter.  A  circuit  breaker  is  without  the 
hazards  of  the  fuse,  there  being  no  molten  metal  when  it  operates. 


Courtesy   of  Trumbull   Electric   Manufacturing   Company. 

Three    pole    knife    switch,    the    supply    end    having    terminals     for 
cartridge  fuses,  which  fuses  may  be  used  on  voltages  as  great  as  250. 


Courtesy   of   Trumbull   Electric    Manufacturing   Company. 

Combination  two  pole  knife  switch  and  cut-out,  installed  in  a  cast 
iron  box  having  hinged  cover.  Generally  installed  at  point  where  service 
wires  enter  the  building. 

The  performance  of  melting  or  blowing  fuses  is  extremely 
variable,  their  behavior  determined  by  the  conditions  and 
surroundings.  If  there  is  a  slight  overload,  as  sometimes 
occurs  from  substituting  60  watt  lamps  for  40  watt  lamps,  for 
example,  the  temperature  of  the  metal  will  gradually  rise  until 


79 

its  melting  point  is  reached,  when  it  will  open  the  circuit 
quietly.  If,  on  the  other  hand,  a  sudden  abnormal  rise  of 
current  is  induced,  say  by  a  short-circuit,  the  fuse  will  tend  to 
disrupt  quickly  and  violently.  An  important  thing  to  remem- 


Courtesy    of    General    Electric    Company. 

A  LINK  FUSE. 

Fuses  are  the  most  elementary  form  for  automatically  opening 
circuits  under  abnormal  conditions.  They  were  first  made  entirely  of 
metals  or  alloys  having  a  lo>w  melting  point. 

ber  is  that  the  carrying  capacity  of  a  fuse  should  never  ex- 
ceed the  safe-carrying  capacity  of  the  smallest  wire  made 
dependent  on  it  for  protection.  An  exception  to  this  rule  may 
be  noted  for  three-wire  systems  with  a  grounded  neutral.  It 
is  felt  that  with*  such  systems  we  may  omit  the  fuse  in  the 
neutral,  or  permanently  grounded  wire,  provided  both  wires 
of  the  ultimate  branch  circuits  controlling  the  lights  are 
properly  protected  by  fuses.  When  cartridge  fuses  are  used, 
the  capacity  in  volts  and  amperes  will  be  found  printed  on  a 
label  pasted  on  the  outside  of  the  tube.  With  plug  fuses,  the 
capacity  in  amperes  will,  on  125  volt  fuses,  be  found  stamped 
on  the  round  metal  contact  in  the  base  of  the  plug,  or  on  its 
cover,  and  on  the  220  volt  plug  fuses  printed  on  a  label  similar 
to  that  used  on  the  cartridge  fuses. 


Courtesy   of  Trumbull   Electric   Manufacturing   Company. 

A  three  pole  knife  switch  with  terminals  for  cartridge  fuses  of  the 
knife-blade  type,  installed  in  a  substantial  metal  cabinet. 


8o 


Courtesy    of    General    Electric    Company. 

A  PLUG  FUSE. 

A  fuse  is  an  "electrical  safety  valve",  in  that  it  serves  to  protect  a 
circuit  from  any  harm  resulting  from  an  undue  overload.  Small  capacity 
fuses  form  an  inexpensive  means  of  protecting  small  circuits.  In  a  plug 
fuse  the  element  is  'with  the  plug  and  never  exceeds  thirty  amperes 
capacity.  With  a  very  few  exceptions  lighting  circuits  should  never  have 
larger  than  ten  ampere  fuses.  Plug  fuses  should  never  be  used  on  voltages 
greater  than  125,  because  of  the  short  distance  between  terminals. 


Courtesy    of    General    Electric    Company. 

A  LINK  FUSE. 

The  simplest  form  of  fuse  consists  of  a  strip  of  metal  fixed  between 
two  end  pieces  to  fit  around  the  terminals.  When  a  fuse  operates  the 
metal  melts  because  of  heating  and  the  molten  metal  will  quickly  ignite 
inflammable  material.  For  this  reason  a  "link  fuse"  should  never  be 
permitted  except  in  a  dust  proof  cabinet  or  on  a  switchboard  in  a  fire 
proof  room. 


Courtesy    of   General    Electric   Company. 

AN  ENCLOSED  FUSE. 

The  enclosed  fuses  are  made  up  of  paper  or  fiber  tubes  filled  with 
some  material  which  is  fireproof  and  which  seems  to  suppress  the  arc 
formed  when  the  fuse,  embedded  in  this  material,  opens  the  circuit.  They 
are  made  for  all  capacities,  those  in  use  in  the  mains  from  the  storage 
batteries  in  the  submarines  of  the  United  States  Navy  being  for  2,300 
amperes.  Because  of  the  action  of  the  powder,  in  suppressing  the  arc, 
these  fuses  were  first  called  "non-arcing  fuses". 


Courtesy    of   General    Electric   Company. 

AN  ENCLOSED  OR  CARTRIDGE  FUSE. 

The  above  illustrates  an  enclosed  or  cartridge  type  of  fuse,  in  which 
the  space  surrounding  the  fuse  wire  is  filled  with  powdered  material. 
Because  of  the  distance  between  the  terminals  this  type  of  fuse  may  be 
used  on  all  commercial  voltages  without  danger  of  arcing  when  the  fuse 
operates. 


8i 

SWITCHES. 

Service  switches  are  generally  of  the  knife-blade  type, 
and  are  mounted  on  either  porcelain,  slate  or  marble  bases. 
They  must  be  so  installed  that  current  may  be  entirely  cut 
off  from  the  inside  wires  for  repairs,  or  in  case  of  fire,  or  other 
accident.  A  single-throw  switch  is  one  having  one  set  of 
contacts,  a  double-throw  being  where  there  are  two  sets  of 
contacts.  Single-throw  switches  must  always  be  installed  so 
that  gravity  will  tend  to  open  rather  than  close  them  since 
otherwise  they  might  fall  and,  by  only  partly  closing,  cause 
arcs  and  burning.  Whenever  practicable,  knife  switches 
should  be  so  wired  that  the  blades  will  be  dead  when  the 
switch  is  open.  Switches  for  the  control  of  motors,  and  where 
the  current  used  is  in  excess  of  20  amperes,  are  usually  of  the 
knife-blade  type. 

Surface  Snap  Switches  are  those  which  are  in  most  com- 
mon use  and  generally  have  a  round  porcelain  base,  with  a 
metal  cover  and  an  operating  handle  in  the  center  of  .the 
cover.  In  use,  they  are  generally  mounted  on  side  walls  and 
the  wires  are  brought  into  them  from  the  back.  It  is  not 
possible  to  fasten  them  securely  to  a  lath-and-plaster  wall 
unless  some  block  is  provided  for  the  screws  to  be  driven 
into.  For  this  reason  a  %"  block  must  be  fastened  between 
the  studs  flush  with  the  back  of  lathing  to  hold  tubes,  and 
to  support  switches  and  fixtures,  as  the  case  may  be.  When 
this  cannot  be  done,  wood  base  blocks,  not  less  than  y^"  in 
thickness,  securely  screwed  to  lathing,  must  be  provided  for 
switches,  and  also  for  fixtures  which  are  not  attached  to  gas 
pipes,  conduit,  or  other  form  of  support.  The  switches  can 
thus  be  securely  and  firmly  screwed  to  the  blocks  and  the 
wires  connected  to  them.  When  the  switch  wires  are  run 
exposed,  the  snap  switches  should  be  mounted  out  from  the 
wall  on  porcelain  sub-bases,  so  that  the  wires  may  enter  the 
switch  from  the  back  without  coming  in  contact  with  the 
wall  on  which  the  switch  is  mounted. 

Flush  switches  are  of  the  type  which  are  inserted  in  the 
wall,  only  the  face  plate,  with  its  handle  or  buttons,  showing. 
That  is  why  they  are  called  flush  switches.  Inasmuch  as  their 
operating  parts  are  concealed  in  the  wall,  they  should  always 
be  set  in  enclosed  iron  boxes,  so,  should  the  switch  go  wrong 
and  arc,  no  flash  or  flame  can  extend  outside  of  the  metal  en- 
closure. The  same  general  requirement  applies  to  all  small 


82 


83 

fittings,  such  as  receptacles,  there  being  the  handy  devices 
into  which  an  attachment  plug,  with  a  flexible  cord  connected 
to  it,  is  inserted  for  the  use  of  a  table  lamp,  fan  motor,  small 
cooking  utensils  and  similar  appliances. 


Courtesy   of.Trumbull   Electric   Manufacturing   Company. 

Three  pole  knife  switch  and  cut-out  installed  in  a  metal  cabinet,  the 
door  of  which  is  so  arranged  that  the  switch  cannot  be  closed  when  the 
door  is  open. 

Sometimes  it  is  desired  to  control  the  same  lights  from 
different  places,  as  in  the  case  of  hall  lights  being  controlled 
from  two  or  more  floors.  This  is  a  practical  thing  to  do  by 
the  use  of  three  and  four  way  switches.  These  switches  are 
always  to  be  considered  as  single  pole  and  are  to  be  so  con- 
nected that  only  one  main  wire  of  the  circuit  feed  is  carried 
into  either  switch.  These  switches,  as  I  have  indicated,  being 
single  pole,  should  never  be  used  on  circuits  of  more  than 
660  watts. 

ELECTRIC  HEATERS. 

Under  this  heading  are  included  all  devices  in  which  use 
is  made  of  heat  developed  by  the  current,  usually  by  causing 
it  to  pass  through  coils  of  wire.  Perhaps  it  may  be  said,  with 
some  force  of  truth,  that  this  branch  of  the  application  of 
electricity  has  developed  more  forms  of  practical  applications, 
in  the  last  few  years,  than  all  of  the  other  branches.  These 
electric  heating  devices  are  in  many  forms,  from  the  house- 
hold chafing  dish  to  the  large  broilers  and  ranges  in  the  grill 
rooms  of  the  modern  hotel.  A  few  years  ago,  I  ate  my  meals 
in  a  restaurant,  in  the  small  town  of  Houlton,  Aroostook 
County,  Maine,  in  which  everything  served  had  been  cooked 
by  electricity.  We  have  curling  irons,  which  of  course  I  do 


not  use,  for  reasons  which  are  obvious ;  pads  to  take  the  place 
of  hot  water  bottles,  which  are  without  the  danger  of  bursting 
and  thus  spilling  the  hot  water  on  the  patient;  radiators  in 
several  forms ;  radiant  grills ;  toasters,  percolators,  egg  codlers, 
hot  water  heaters,  flatirons  and  an  almost  endless  variety  of 
devices,  all  of  which  present  the  same  hazards  as  other  heaters 
of  equal  capacity,  except  that  the  match  hazard  or  the  ex- 
plosion hazard,  where  gas  is  used  for  cooking  and  heating, 
are  eliminated. 

It  is  essential  that  these  devices  be  protected  by  fuses  in 
the  branch  supply  circuits  and  also  be  controlled  by  switches 
which  will  indicate  whether  or  not  the  current  is  "on"  or 
"off."  They  should  never  be  concealed  without  special  per- 
mission, and  when  concealed  should  be  arranged  in  such  a 
manner  that  the  heater  could  burn  up  without  damage  to  sur- 
rounding objects. 

Experience  has  shown  the  fire  underwriting  interests  that 
the  portable  heating  devices  are  much  more  hazardous  than 


Courtesy   of   Commissioner  James    E.    Cole,    Wire   Dept.,    Boston,    Mass. 
Dining  room  in  a  residence  in  Boston,  Mass. 


Courtesy^of  CommissionerJ'James'E.   Cole,   Wire  Dept.,  Boston,  Mass. 

Butler's  pantry  in  same  residence. 

Fire  caused  by  defective  installation  of  electric  plate  warmer,  with 
a  total  fire  insurance  loss  of  $180,198.06. 

those  of  the  stationary  type.  This  is  not  because  of  a  possible 
defective  installation,  since  the  stationary  heaters  may  be 
suitable  protected,  while  it  is  not  always  possible  with  those 
of  the  portable  type.  The  electric  flatiron  is  perhaps  the 
cause  of  more  trouble  and  danger  from  fire  than  any  other 
form  of  heater,  a  fact  due  entirely  to  use  and  management 
rather  than  to  installation  difficulties.  The  temperature  of 
the  iron  required  for  ironing  of  damp  fabrics  is  necessarily 
high  and  if  the  iron  is  left  with  current  on  and  is  not  in  use 
it  will  become  red-hot  in  from  ten  to  twenty  minutes.  If  it  is 
left  on  a  table  or  on  clothing,  a  fire  is  to  be  expected. 

All  portable  heaters,  if  they  require  over  250  watts  of 
energy  should  have  approved  "heater  cord"  which  consists  of 
stranded  copper  conductors  with  a  thin  rubber  and  a  thick 
asbestos  yarn  covering  over  each,  with  good  braid  over  all. 
In  factories,  shops,  clothing  manufactories  and  manual  train- 
ing schools,  where  a  large  number  of  flatirons  and  other  port- 
able heaters  are  used,  the  circuits  supplying  them  should  be 


86 

so  arranged  with  switches  that  any  department  or  section  can 
be  cut-off  when  not  in  use. 

Unless  flatirons  are  small,  they  should  not  be  used  on  the 
ordinary  lighting  circuits,  as  they  would  overload  such  cir- 
cuits and  cause  heating  of  the  smallest  wTire  on  the  circuit, 


Courtesy    of    Crouse-Hinds    Company. 

Method  suggested  for  the  installation  of  an  electric  flatiron,  the 
fitting  having  a  snap  switch  and  fuses  for  the  protection  of  the  flexible 
cord  and  flatiron.  Within  this  fitting  will  be  seen  the  tell-tale  lamp,  the 
glow  of  which  indicates  whether  or  no  current  is  flowing  through  the  iron. 

which  wire  is  in  the  lighting  fixtures.  The  lighting  fixtures 
and  sockets  are  not  substantially  enough  constructed  to  per- 
mit of  the  rough  usage  which  they  will  receive  if  these  devices 
are  connected  to  them.  *  Electric  flatirons  should,  in  all  in- 
stances, be  provided  with  approved  stands  to  receive  the  irons 
when  not  in  use. 


Courtesy    of    Crouse-Hinds    Company. 

A  luminous  radiator  connected  to  circuit  wires  in  conduit  by  the 
means  of  flexible  cords,  an  attachment  plug  and  receptacle,  the  latter 
secured  to  a  receptacle  fitting.  Heating  devices  of  this  type  should  be 
kept  well  away  from  the  woodwork  of  the  room. 


88 

METHODS  OF  WIRING. 

Various  methods  have  been  standardized  for  the  install- 
ing of  wires  for  low  potential  systems,  which  at  the  present 
time  includes  all  systems  of  550  volts,  or  less.  We  shall  con- 
sider these  methods  separately. 

OPEN  WORK: — This  method  of  wiring  is  used  very 
extensively  on  ceilings  in  mills,  factories,  stores,  and  for  heavy 
conductors  for  feeders,  mains,  etc.,  in  tunnels  and  in  similar 
places.  Where  the  appearance  of  exposed  wiring  is  not  ob- 
jectionable, this  is  one  of  the  safest,  cheapest,  and  best  meth- 
ods of  wiring.  In  fact,  if  properly  done,  its  appearance  is  far 
from  objectionable. 

In  dry  places,  up  to  300  volts,  it  is  permitted  to  support 
the  wires  on  porcelain  cleats  which  raise  the  wires  */2  inch 


Courtesy    of    Crouse-Hinds    Company. 

Open  wiring  entering  conduits  through  terminal  fittings,  which  have 
a  separately  insulated  opening  for  each  wire. 


89 

from  the  surface  wired  over,  the  wires  being  2^2  inches  apart, 
and  for  voltages  between  300  and  550  the  distance  is  to  be 
one  inch,  the  wires  being  kept  four  inches  apart.  The  distance 
between  supports  should  not  be  greater  than  4l/2  feet,  and  if 
the  wires  are  liable  to  be  disturbed,  this  distance  should  be 
decreased.  For  such  work,  the  so  called  slow-burning  in- 
sulation may  be  used.  In  damp  places,  wrire  having  a  rubber 
insulation  must  be  used  and  the  supports  must  raise  the  wires 
at  least  one  inch  from  the  surface  wired  over,  the  wires  to  be 
kept  2l/2  inches  apart  in  systems  up  to  300  volts,  and  four 
inches  apart  for  systems  between  300  and  550  volts.  The 
distance  between  supports  to  be  such  as  will  prevent  the  wires 
being  disturbed,  but  never  less  than  4^  feet. 

MOULDING  WORK:— Moulding  is  now  called  "race- 


Courtesy   of   Crouse-Hinds   Company. 

A  well  arranged  conduit  installation  from  a  distributing  cabinet  to 
the  various  outlets.  The  use  of  the  peculiar  fittings  make  possible  the 
absence  of  long  bends,  thus  keeping  the  conduits  close  to  each  other. 


90 

ways"  and  is  sometimes  used  where  the  use  of  cleat  work 
would  be  objectionable  from  the  standpoint  of  appearance,  and 
where  it  would  be  impracticable,  difficult  or  expensive  to  in- 
stall concealed  wiring.  Raceways,  either  wood  or  metal, 
should  never  be  installed  in  a  damp  place  nor  should  they  be 
concealed.  Wire  having  a  rubber  insulation  must  be  used 
and  splices  in  the  wrire  should  not  be  made.  Where  taps  or 
extensions  of  wire  are  necessary,  fittings  for  this  purpose 
should  be  used.  In  metal  raceways,  single  circuits  should  be 
limited  to  1,320  watts  and  the  several  lengths  of  the  raceways 
should  be  electrically  bonded  and  effectively  and  permanently 
grounded. 

CONDUIT  WORK:— The  requirements  of  a  good  con- 
duit are  first,  it  should  be  fire-proof.  There  exists  in  every 
electric  conduit  for  light  or  power  the  elements  necessary  to 
cause  fire,  and  every  precaution  should  be  taken  to  prevent 
the  conduit  from  igniting  and  burning.  In  the  second  place, 
it  should  be  moisture  proof,  while,  in  the  third  place,  the 
conduit  should  be  strong  mechanically.  It  should  resist  nails, 


Courtesy    of    Crouse-Hinds    Company. 

Installation  of  conduits  with  special  fittings   for  electric  flatirons  in 
a  tannery-. 


hard  blows,  and  should  not  easily  be  flattened  by  being  walked 
upon  or  by  having  wheelbarrows  run  over  it.  Lastly,  the 
conduit  should  withstand  a  "short-circuit"  on  the  wires  which 
they  contain  without  disrupting.  Wires  having  a  rubber  in- 
sulation should  be  used  in  conduits  and  the  conduit  system 
should  be  grounded. 

ARMORED  CABLES:— As  the  name  implies,  this 
method  consists  of  the  wires  being  protected  by  a  flexible 
steel  armor  which  is  wound  over  the  rubber  insulated  wires. 
It  is  much  more  convenient  to  install,  for  concealed  wiring, 
than  rigid  conduit,  to  which  it  is  inferior  in  one  respect,  since 
the  wires  cannot  be  withdrawn  should  it  be  advisable  to  do 
so.  As  in  conduit,  the  armored  cable  systems  should  be 
grounded. 


Customary   way   of  fastening  flexible   steel-armored  cable 
in  junction   or  outlet   box. 

CONCEALED  KNOB  AND  TUBE  WORK:— This 
method  of  wiring  is  used  where  first  cost  is  of  the  greatest 
importance.  In  this  method,  the  wires  are  run  concealed 
under  floors  and  in  partitions  supported  on  porcelain  knobs 
and  insulated  where  they  pass  through  floors  and  beams  by 
porcelain  tubes.  The  knobs  are  used  where  the  conductors 
run  parallel  to  the  joists  and  for  vertical  runs,  and  the  tubes 
are  used  wrhere  the  wrires  pass  through  the  joists  and  plates 
or  heads  of  partitions.  Flexible  tubing  is  used  at  outlets  to 
protect  the  wires.  Here  again  rubber  insulation  is  required 
and  the  wires  are  to  be  supported  on  knobs  which  raise  the 
wires  one  inch  from  the  surface  wired  over,  the  supports  be- 


92 

ing  not  greater  than  4^  feet  apart.  While  this  method  may 
be  open  to  objections,  mechanical  injury  by  artisans  installing 
their  own  work  or  making  repairs,  it  is  reasonably  safe,  and 
does  tend  to  drive  out  the  match  hazard.  It  is  much  safer 
than  kerosene  or  gas  which  it  replaces. 


One  Inch  Separation 
From  Surf  ace  Wired  Over 


Rubber-  Insulake/ 
Conductors 


.. 

, •"  Insulated 
Conductors 


>/s 


I  Undesirable  Arranqement 


- Desirable  Arrangement 


FIXTURE  WIRING:— Fixtures  should  be  wired  with 
rubber  insulated  wire,  except  where  the  lighting  units  develop 
excessive  high  temperatures,  and  should  be  insulated  from 
the  gas  piping  and  other  grounded  metal  work  of  the  building. 
Under  some  conditions  fixtures  may  be  installed  without  in- 
sulating from  the  grounded  metal  parts  of  the  building,  pro- 
viding the  insulation  of  the  fixture  wire  is  the  same  as  that 
of  the  circuit  wires  and  specially  designed  sockets  are  used. 
The  ordinary  wire  cannot  be  used  in  the  average  lighting 


Showing  Application  of  "Plaster  or  Mud  Tubes.' 


93 

fixture  because  of  the  thickness  of  its  insulation,  so  a  wire 
having  a  thinner  insulation  is  permitted. 

SOCKETS : — Sockets  used  in  stables  or  other  damp 
places,  should,  preferably  be  of  the  porcelain  type.  The  or- 
dinary key  socket  should  be  considered  as  a  single-pole 
switch  and  should  never  be  installed  where  there  are  inflam- 
mable gases  or  vapors  which  could  be  ignited  by  the  spark 
when  turning  off  the  current  by  the  key,  or  switch,  in  the 
socket.  In  such  cases,  the  lamp  should  be  in  a  vapor  proof 
globe  as  a  protection  to  the  lamp  and  a  keyless  socket  used, 
such  socket  to  be  controlled  by  a  switch  which  must  be 
located  beyond  reach  of  the  gases  and  vapors. 


Qfl 


FLEXIBLE  TUBING  ON  OUTLET  WIRES. 

FLEXIBLE  CORD:— The  proper  and  intended  use  of 
flexible  cord  connected  with  electrical  installations  has  been 
of  very  great  value  in  aiding  the  application  of  electricity  and 
nothing  has  caused  as  much  harm  as  through  its  misuse.  The 
ordinary  flexible  cord  consisting  of  two  stranded  conductors, 
each  conductor  insulated  with  rubber  and  surrounded  with  a 
cotton  or  silk  braid,  is  intended  to  be  used,  other  than  in  a 
fixture,  on  devices  which  hang  freely  pendant  in  the  air.  It 


Socket 


Method   of   installing   short   pendent   in   damp   location. 


94 

should  never  be  run  over  ceilings,  down  sidewalls  or  parti- 
tions, or  through  the  floors.  Nor  should  it  be  used  for  port- 
able devices  nor  in  show  windows.  For  portable  purposes  a 
flexible  cord  similar  to  the  one  I  have  described,  but  sur- 
rounded by  a  tough  braided  outer  covering,  should  be  used 
that  the  conductors  may  be  protected  from  the  mechanical 
abuse  which  frequently  results.  Flexible  cords  should  never 
be  used  in  damp  places,  nor  should  they  be  hung  on  nails, 
metal  work  or  stapled  to  wood  work.  Adjusting  devices  that 
tend  to  destroy  the  insulation  of  the  flexible  cord  should  not 
be  used. 


Method  of  installing  a  lighting  fixture  on  a  gas  pipe,  showing  the 
protection  of  the  circuit  wires  with  flexible  tubing,  the  insulating  joint 
and  the  insulating  tubing  on  the  gas  pipe  above  the  joint. 

ARC  LAMPS,  LOW  POTENTIAL  CIRCUITS :— The 
progress  made  in  the  high-efficiency  incandescent  lamp  has 
made  the  arc  lamp  almost  unnecessary  for  interior  lighting. 
When,  however,  arc  lamps  are  to  be  used,  common  practice 
provides  for  these  lamps  to  be  supplied  from  the  ordinary 
no  or  220  volts  circuit.  They  should  be  considered  the  same 
as  if  supplied  by  series  circuits,  it  being  necessary  to  provide 
them  with  globes,  spark  arrestors  and  wire  netting. 


Part  No.  5. 

In  our  preceding  lectures,  an  effort  was  made  to  point  out 
electrical  hazards  which  might  be  found  in  most  any  type  of 
installation.  This  evening,  we  will  endeavor  to  make  clear 
hazards  which  can  be  found  in  such  installations  having 
special  features  of  use,  materials  and  appliances. 


95 


96 

VAPOR  LAMPS. 

An  enclosed  mercury  vapor  lamp  consists  essentially  of 
two  separate  elements,  the  tube  or  light-giving  part,  and  the 
operating  mechanism.  The  tube  is  of  clear  glass  of  varying 
length,  from  21  inches  to  55  inches,  with  electrodes  at  each 
end  and  containing  a  small  quantity  of  metallic  mercury.  The 
air  is  exhausted  and  the  tube  then  sealed.  The  mercury  is 
held  in  the  large  bulb  at  one  end  of  the  tube,  and  serves  as 
the  negative  electrode,  the  tube  being  always  so  suspended 
that  this  bulb  is  the  lowest  part  of  the  tube.  The  positive 


Courtesy    of    Crouse-Hinds    Company. 

Installation  of  electric  lights  in  a  location  where  inflammable  gases 
are  present,  the  lamps  being  located  in  vapor  proof  globes. 

electrode  is  a  small  iron  cup  at  the  other  end  of  the  tube.  The 
current  is  conveyed  to  the  electrodes  through  platinum  wires 
sealed  in  the  glass.  The  current,  passing  from  the  positive 
electrode  to  the  negative,  vaporizes  some  of  the  mercury  and 
causes  the  vapor  to  become  luminous.  That  these  lamps, 
which  are  essentially  intended  to  be  used  on  direct-current 
systems,  may  be  used  on  alternating-current  systems,  an  auto 
transformer  is  used.  The  quality  of  the  light  is  peculiar,  it 


97 

containing  no  red  rays  and  has  a  peculiar  bluish-green  color. 
The  auto-transformer  and  resistance  used  with  these 
lamps  should  be  treated  as  possible  sources  of  heat  and  must 
always  be  enclosed  in  non-combustible  cases  and  must  have 
all  openings  in  their  casings  covered  with  fine  wire  gauze 
when  installed  in  locations  where  there  are  flyings  of  lint  or 
other  combustible  materials. 

HIGH  POTENTIAL 
VACUUM  TUBE  SYSTEMS. 

While  this  form  of  lighting  is  not  in  general  use,  the  Code 
has  made  provision  to  safeguard  the  several  hazards  involved. 
In  theory  it  is  similar  to  the  Geissler  tube  and  resembles  the 
mercury  vapor  lamp  in  that  it  consists  of  a  conducting  vapor 
enclosed  in  a  tube  and  owes  its  illuminosity  to  the  incan- 
descent particles  of  matter  in  the  vapor  stream.  These  tubes 
vary  in  length  from  40  to  200  feet  of  continuous  glass  tubing. 
The  conducting  gas  is  supplied  to  this  tube-nitrogen,  emitting 
a  yellow  light,  gives  the  highest  efficiency,  while  carbon 
dioxide  gives  a  white  light  differing  little  from  daylight. 
When  the  tube  is  fed  with  air  alone,  the  light  is  a  pale  pink 
color. 

The  terminals  of  the  tube  are  brought  to  a  terminal  box 
and  sealed  upon  carbon  electrodes  which  serve  the  purpose 
of  conducting  the  electricity  to  the  gas.  This  terminal  box 
contains  a  step-up  transformer  with  its  high  side  connected 
to  the  tube,  and  a  regulating  device  to  control  the  density  of 
the  vapor  in  the  tube.  This  glass  tube  must  be  so  installed 
as  to  be  free  from  mechanical  injury  or  liability  to  contact 
with  inflammable  materials.  The  high  potential  coils  and 
regulating  apparatus  must  be  installed  in  a  steel  cabinet  not, 
less  than  %0  incn  m  thickness ;  same  to  be  well  ventilated  in 
such  a  manner  as  to  prevent  the  escape  of  any  flame  or  sparks, 
in  case  of  burnout  in  the  various  coils.  To  protect  against 
dangerous  shocks,  any  openings  in  the  box  near  the  high- 
voltage  parts  should  be  effectively  screened  or  protected  by 
other  suitable  means. 

GAS  FILLED 
INCANDESCENT  LAMPS. 

This  is  the  highest  development  of  the  incandescent  elec- 
tric lamp.  Nitrogen  or  Argon  gas  is  used  in  the  bulbs  which 


98 

greatly  increases  the  illuminating  power  of  the  lamp  and  de- 
creases the  consumption  of  energy.  In  the  old  carbon  filament 
lamp,  3^2  watts  of  energy  were  required  for  each  candle- 
power  the  lamp  gave.  The  old  commercial  unit,  the  16  candle- 
power  lamp  required  55  watts  of  energy,  whereas,  the  so-called 
gas-filled  lamp,  in  some  instances,  requires  but  J/£  watt  for 
each  candle-power.  To  achieve  this  result,  a  hazard  was  in- 
troduced in  the  intense  heat  which  is  given  off  by  these  lamps. 
They  must  never  be  used  in  a  show  window  or  in  other  locali- 
ties where  inflammable  material  is  liable  to  come  in  contact 
with  the  lamp  equipment  except  when  used  in  connection  with 
approved  fixtures  where  the  temperature  of  any  exposed 
portion  of  same  does  not  exceed  200  degrees  Fahr.  If  the 
lamp  is  above  200  watts  normal  capacity,  it  must  never 'be 
used  in  the  medium  based  sockets  or  receptacles.  If  above 
100  watts,  must  not,  if  provided  with  a  shade,  reflector,  fixture 
or  other  enclosure  above  the  socket,  be  used  in  either  medium 
or  Mogul  base  types  of  sockets  or  receptacles  having  fibre  or 
paper  linings.  When  the  temperature  from  these  lamps  ex- 
ceeds 120  degrees  Fahr.,  the  fixtures  within  buildings  must  be 
wired  with  conductors  of  approved  slow-burning  or  asbestos 
covering.  Where  fixtures  are  placed  outside  of  buildings, 
approved  rubber  insulated  wires  is  required. 

OIL  TRANSFORMERS. 

Must  not  be  placed  inside  of  any  building,  except  central 
and  sub-stations,  unless  by  special  permission,  and  only  then 
when  they  are  installed  in  fire-proof  vaults,  as  described  in  a 
preceding  lecture. 

TRANSFORMERS,  AIR  COOLED. 
INSIDE  USE. 

There  are  several  types  of  air-cooled  transformers  which 
are  permitted  within  buildings  because  of  their  low  capacity 
ratings.  Some  electric  lighting  companies  have  a  low-poten- 
tial contract  system  in  which  no  recording  watt  meter  is  used. 
A  special  potential,  however,  is  desired  that  the  consumer  may 
not  use  more  current  than  has  been  contracted  for.  That  the 
desired  potential  or  voltage  may  be  obtained,  an  air-cooled 
transformer,  called  an  auto-transformer,  is  installed  within 
the  building,  stepping  the  potential  down  from  no  volts  to 


99 

55  volts  and  sometimes  to  27  volts.  These  transformers  must 
always  be  considered  as  possible  sources  of  heat  and  should 
be  enclosed  in  iron  cases.  They  must,  also,  be  mounted  on 
slate  or  marble  bases  and  should  never  be  installed  in  closets 
where  there  will  be  combustible  and  inflammable  materials. 

Electrical  transformers  for  stepping  down  alternating- 
currents  of  the  usual  lighting  circuit  to  a  much  lower  potential 
for  operating  electric  toys  and  the  ringing  of  the  ordinary 
house  bells  are  in  general  use.  It  can  be  said  that  small 
electrical  devices  used  on  a  few  volts  may  have  no  limitations 
as  to  cheapness.  But  it  is  quite  otherwise  with  the  toy  trans- 
former that  is  connected  to  the  no  volt  circuit.  It  is  of  the 
utmost  importance  that  toy  transformers  be  made  as  fool-proof 
as  possible.  They  must  never  be  connected  to  systems  of 
greater  than  125  volts,  nor  should  the  low-voltage  rating  ex- 
ceed 25  volts.  The  input  measured  by  a  watt  meter  in  the 
high  voltage  side,  when  the  low-voltage  terminals  are  short- 
circuited,  must  not  be  more  than  25  watts. 

DECORATIVE  LIGHTING  SYSTEMS. 

Decorative  lighting  by  means  of  incandescent  lamps  is 
often  desired  either  inside  or  outside  buildings.  The  chief 
hazards  of  such  work  lie  in  the  use  of  inferior  materials  hastily 
'  put  together  and  poorly  located  and  fused.  The  voltage  of 
such  systems  should  never  exceed  150  volts  and  not  more 
than  1,320  watts  of  energy  should  ever  be  permitted  to  be 
dependent  upon  a  single  cut-out.  It  would  be  improper  to 
take  current  for  such  systems  from  ordinary  outlets,  since  by 
so  doing,  the  wires  to  the  outlets  would  be  overloaded  and 
the  proper  fuses  for  the  wires  will  have  to  be  replaced  by 
others  of  too  great  capacity  to  furnish  safe  protection.  The 
supply  should  be  taken  only  from  points  on  the  circuit  where 
the  correct  fusing  and  wiring  can  be  provided  for. 

The  wires  are  often  made  to  serve  as  supports  for  mer- 
chandise of  very  inflammable  material  and  the  conditions  are 
excellent  for  a  rapidly  spreading  fire  if  any  electrical  failure 
should  occur.  Incandescent  lamps  frequently  lie  against  in- 
flammable material  and  the  fact  that  such  an  installation  is 
"temporary"  does  not  lessen  the  hazards  as  long  as  it  is  in 
operation  and  should  not  in  any  sense  be  considered  as  an 
excuse  for  allowing  practices  which  are  known  to  be  danger- 
ous. 


100 

ELECTRICALLY  OPERATED  ORGANS. 

There  is  an  electrical  fire  hazard  in  those  parts  of  elec- 
trically operated  organs  which  are  employed  for  the  control 
of  the  sounding  apparatus,  such  as  the  reeds,  pipes,  drums, 
etc.,  and  the  keyboards  on  the  consols.  The  electrical  energy 
may  be  from  a  battery  or  a  self-excited  generator  rated  at  not 
over  15  volts.  The  conductors,  which  may  be  bunched  in  a 
cable,  must  have  either  rubber,  cotton  or  silk  insulation. 
When  in  cable  form,  unless  installed  in  conduit,  the  outside 
covering  must  either  be  flameproof  or  covered  with  a  closely 
wound  fireproof  tape.  The  circuits  must  be  so  subdivided  and 
protected  at  the  generator  by  approved  enclosed  fuses  of  not 
over  thirty  amperes  capacity  that  every  wire  will  be  protected 
by  one  or  more  such  fuses.  By  such  fusing  at  the  required  15 
volts,  each  circuit  would  then  be  limited  to  450  watts. 

THEATRES  AND 

MOTION  PICTURE  ESTABLISHMENTS. 

These  risks,  with  their  electrical  installations,  require 
careful  attention  because  of  the  fire  and  life  hazards  involved,, 
the  latter  being  of  the  greatest  importance.  In  the  fully 
equipped  theatre,  we  have  not  alone  the  fire  hazard  from 
electrical  causes,  but  the  hazards  of  scenery,  dressing  rooms, 
paraphernalia  and  the  numerous  devices  for  producing  stage 
effects.  What  are  termed  moving  picture  establishments,  in 
many  instances,  are  without  the  dressing  rooms,  scenery  and 
the  other  hazards  of  a  theatre,  but  have  a  hazard,  while  not 
electrical,  of  the  greatest  concern.  These  moving  picture 
enterprises  have  often  been  established  in  rooms  originally 
intended  for  stores  and  the  equipment  has  been  of  the  poorest 
character.  This  condition  has  been  greatly  improved  as  ex- 
perience has  been  gained  and  has  been  made  the  subject  of 
legislation  by  state,  municipal  and  insurance  interests.  The 
requirements  for  the  electrical  equipments  in  both  of  these 
amusement  enterprises  are  the  same.  In  brief,  they  provide 
for  the  following: 

FIRST :— There  shall  be  two  services  of  supply  for  the 
lighting  of  the  building,  one  to  care  for  the  equipment  on  the 
stage  and  the  general  lighting  for  the  auditorium;  the  other 
service,  which  must  be  entirely  independent  of  the  service  for 
the  general  equipment,  for  the  supply  for  the  emergency  or 


ioi  '/;  ^  v 

exit  lights.  This  provision  bears  but  little  upon  the  fire 
hazard,  but  is  intended  to  provide  illumination  sufficient  for 
the  audience  to  pass  from  the  building  under  any  and  all 
conditions  liable  to  exist,  even  when  the  general  illuminating 
system  has  been  rendered  useless.  This  would  aid  in  pre-> 
venting  a  panic. 

SECOND: — The  wiring  on  the  stage  and  the  concealed 
wiring  in  the  building  must  be  in  metal  conduits  or  armored 
cables.  Should,  however,  any  of  the  wiring  be  exposed  in  the 
auditorium,  stairways  or  lobbies,  such  wiring  may  be  in 
conduit,  armored  cables  or  metal  raceways.  All  of  the  stage 
equipment,  as  well  as  the  house  lighting,  except  the  emergency 
or  exit  lights,  are  controlled  from  a  switchboard  located  on 
the  stage.  If  the  switchboard  is  on  the  level  of  the  stage,  a 
railing  is  required  across  the  front  of  the  switchboard  to  pre- 
vent performers  coming  in  contact  with  the  exposed  live 
parts  of  the  equipment.  The  dimmers,  footlights,  borders  and 
all  equipment  are  designed  and  installed  with  the  view  of  pre- 
venting contact  with  scenery  or  injury  through  the  regular 
use  of  the  equipment.  The  proper  installation  of  all  the  stage 
devices,  many  of  which  are  used  for  special  effects,  is  such  an 
important  feature  of  the  safety  of  the  theatre  that  special 
rules  are  established  for  portable  conductors  for  lights  on 
scenery,  for  festoons,  and  for  many  special  effects. 

MOTION  PICTURE  MACHINES. 

The  motion  picture  machines  in  use  to-day  represent  the 
combined  experience  of  a  number  of  efforts  and  are  to  be 
found  in  use  in  most  of  the  theatres  for  entertainment  and  in 
a  number  of  our  institutions  of  learning  for  educational  and 
•  scientific  purposes.  It  might  be  described  as  an  intricate 
stereopticon  having  an  arc  light  in  a  metal  housing,  as  an 
illuminant.  It  does  not,  as  many  suppose,  reproduce  photo- 
graphs of  motion  but  does  show  a  number  of  separate  and 
distinct  pictures,  but  the  speed  with  which  these  pictures  are 
shown  upon  the  screen  deceives  the  eye  and  they  appear  as 
if  in  actual  motion,  rather  than  separate  pictures  with  even 
the  light  being  withdrawn  from  the  screen,  between  the 
pictures,  for  a  small  fraction  of  time.  This  deception,  or 
optical  delusion,  is  accomplished  by  a  revolving  shutter  by 
which  the  light  on  the  screen  is  cut  off  during  the  movement 
of  the  film  and  consists  of  three  wings,  one  of  which  is  rela- 


Courtesy    of    Nicholas    Power    Company. 

Power's    Cameragraph    No.    6B    with   motor    drive, 
represents  the  progress  made  in  this  science. 


This    machine 


Courtesy    of   Nicholas    Power    Company. 

Mechanism  showing  the  automatic  shutter,  film  shields,  drive  crank 
and  film  of  Power's  No.  6  Cameragraph. 


104 

tively  wide  and  obstructs  the  light  on  the  screen  during  the 
movement  of  the  film,  the  other  two  relatively  narrow  and 
adapted  to  interrupt  the  light  twice  while  the  picture  is  on  the 
screen,  so  as  to  prevent  flicker.  The  pictures  on  the  film  must 
be  in  absolute  synchronism  with  this  shutter.  This  is 
accomplished  by  sprocket  wheels  over  which  the  film  passes 
from  the  upper  magazine  through  the  head  of  the  machine  to 
the  gate,  or  aperture,  through  which  the  condensed  light  rays 
strike  the  film.  The  film  continues  over  other  sprockets  to 
the  lower  magazine.  The  magazines,  sprockets,  revolving 
shutter  and  gate  at  the  aperture  are  all  connected  by  gears 
and  belts  to  the  source  of  power  which  is  generally  a  small 
motor. 

The  hazard  is  in  the  film  which  is  made  of  Nitro-Cellulose 
and  is  extremely  inflammable,  igniting  without  contact  with  a 
flame  at  about  210  degrees  Fahr.  These  films  are  on  metal 
reels  and  are  from  500  feet  to  2000  feet  in  length.  The  com- 
mercial film  is  i-ll/32  inches  wide  having  perforations  on  both 
sides,  such  perforations  corresponding  to  the  sprocket  wheels, 
which  have  5.4  teeth  to  an  inch.  There  are  16  pictures  on  I 
foot  of  film.  These  films  should  always  be  kept  in  metal  cases 
having  tight  fitting  covers  and  should  never  be  exposed  or 
operated  unless  in  a  booth  constructed  of  fire-resisting  ma- 
terial, which  booth  must  be  ventilated  to  the  outside  air  that 
gases  from  a  burning  film  may  be  quickly  dissipated  by  the 
means  of  an  electric  exhaust  fan.  All  openings  should  be 
equipped  with  automatic  shutters  suspended  from  a  fusible 
link.  While  it  was  not  unusual  in  the  earlier  days  of  the 
motion  pictures  to  have  the  films  take  fire,  the  hazard  has 
been  so  well  safeguarded,  largely  through  a  more  intelligent 
class  of  operators,  that  rarely  do  we  hear  of  such  fires. 

The  booths  in  which  the  moving  picture  machines  are 
operated  are  generally  made  of  an  angle  iron  frame,  the  sides 
and  tops  of  which  are  covered  with  asbestos  building  lumber, 
generally  called  transite,  %  inch  thick,  securely  bolted  to  the 
frame.  The  floor  is  covered  with  the  same  material,.  tys  inch 
thick. 

FILMS. 

The  non-inflammable  film,  which  does  not  burn  with  a 
flame  and  which  does  not  easily  ignite,  has  not  been  the  com- 
mercial success  hoped  for  and  is  but  little  used  in  the  standard 


sized  machines  operated  in  the  theatres  and  in  other  public 
places.  There  is,  however,  a  smaller  equipment  which  is  per- 
mitted to  be  used  without  the  booth  required  for  the  larger 
equipments.  These  miniature  equipments  require  a  special 
sized  film,  and  will  not  take  the  films  of  the  commercial  size. 
These  equipments  must  never  consume  more  than  600  watts. 
The  films  used  are  of  an  approved  slow-burning  type  having 
a  permanent  distinctive  marker. 


Courtesy    of    Nicholas    Power    Company. 

Complete  equipment  of  Power's  Cameragraph  No.  6,  which  is  a  hand 
driven  machine. 


io6 


Courtesy  of  H.   W.   Johns   Manville   Co. 

A  standard  booth  for  a  moving  picture  machine  equipment.  This 
consists  of  frames  of  angle  iron,  covered  with  transite,  or  asbestos 
lumber,  the  frames  being  bolted  together.  At  the  bottom  of  4  sides  of 
the  booth  are  openings  covered  with  wire  cloth  of  fine  mesh  for  ventilating 
purposes.  A  metal  vent  pipe  extends  from  the  top  of  the  booth  to  the 
outside  air. 

MOTION  PICTURE  FACTORIES, 
STUDIOS  AND  EXCHANGES. 

The  greatest  hazard  of  the  moving  picture  industry  is  to 
be  found  in  the  Factories,  Studios  and  Exchanges  because  of 
the  great  amount  of  film  used  and,  frequently,  the  limited 
time  used  in  handling  them.  A  Moving  Picture  Factory, 
Studio  or  Exchange  is  considered  as  that  building  or  portion 
of  a  building  in  which  moving  picture  films  are  manufactured, 
exposed,  developed,  printed,  rewound,  repaired,  stored,  etc. 
The  electrical  equipment  must  be  on  lines  similar  to  those 
required  for  a  theatre,  the  lamps  to  be  so  installed  that  they 
could  not  come  in  contact  with  a  film.  All  current-breaking 
devices  for  the  electrical  equipment  must  be  enclosed  in  ap- 
proved dustproof  and  fireproof  cabinet,  while  all  motors  must 
be  of  the  induction  type.  Where  Direct  Current  motors,  how- 
ever, must  be  used,  they  must  have  enclosed  commutators. 
The  films  must  be  kept  in  safes,  vaults  or  cabinets,  which 
must  be  ventilated  to  the  outside  air.  All  scrap  or  waste  shall 
be  kept  under  water,  in  self-closing  standard  metal  cans  or 
their  equivalent  and  any  cement  having  collodion  and  amyl 
acetate  or  similarly  inflammable  compounds  shall  not  exceed 


the  quantity  required  for  one  day,  inside  of  the  building,  and 
shall  be  limited  to  one  gallon. 


Courtesy    of   the   H.    W.    Johns    Manville   Company. 

A  moving  picture  booth  of  the  portable  type. 

OUTLINE  LIGHTING. 

This  is  a  form  of  decorative  lighting,  which  is  most  gen- 
erally installed  in  a  permanent  form,  in  which  rows  of  incan- 
descent lamps  are  used  on  the  exterior  of  buildings  to  outline 
some  pf  the  architectural  features.  The  former  method  of 
lighting  the  dome  on  the  Capitol,  at  Hartford,  was  through 
outline  lighting,  in  which  each  lamp  had  its  distinctive  place. 
Such  systems  are  sometimes  installed  inside  of  buildings  when 
the  regular  rules  for  inside  installations  are  to  be  followed. 
Outline  lighting  on  the  outside  of  buildings,  however,  may 
have  special  characteristics.  Only  systems  under  550  volts 
may  be  used  in  either  open  work  or  in  conduit.  When  open 
work  is  used,  the  rules  for  wiring  in  damp  places  should  be 
followed.  These  rules,  you  will  recall,  require  that  the  wires 
be  2^2  inches  from  each  other  and  I  inch  from  the  surface 
wired  over.  The  circuits  for  outline  lighting  should  have 
their  own  separate  switches  and  fuses,  which  must,  if  installed 
on  the  outside  of  buildings,  be  installed  in  approved  weather- 
proof cabinets.  The  switches  must  never  be  of  the  single-pole 
type  and  circuits  must  be  so  arranged  that  not  more  than  1320 
watts  will  be  dependent  upon  one  cut-out. 


io8 

/ 

ELECTRIC  SIGNS. 

The  subject  of  electric  signs  has  developed  into  a  science 
of  itself.  It  is  not  my  purpose  to  pass  upon  the  general 
hazards  of  large  signs  and  the  obstruction  they  offer  to  fire- 
men. Signs  should  be  substantially  built  because  of  their 
exposure  to  the  high  winds  and  other  elements.  Preferably, 
they  should  be  constructed  of  metal.  The  wires  should  have 
rubber  insulation  and  should  be  soldered  to  the  terminals  of 
receptacles.  The  flashing  or  animating  is  accomplished  by  a 
machine  known  as  a  "flasher",  which  is  really  a  number  of 
switches  operated  by  a  motor-driven  drum. 

The  location  of  a  sign  flasher  should  be  such  as  to  remove 
it  from  chance  of  accidental  injury  or  tampering,  to  permit 
the  direct  and  well  arranged  running  of  circuits  to  it,  and  to 
render  it  accessible  for  cleaning,  adjusting  and  inspecting.  A 
flasher  should  never  be  installed  in  a  closet  or  other  inaccess- 
ible place,  and  should  be  installed  in  a  strong  metal  cabinet. 


Courtesy  of  Crouse-Hines  Co. 

The  building  pictured  above  is  the  City  Hall  at  New  Orleans,  La. 
Every  lamp  in  the  outlining  is  held  in  a  receptacle,  mounted  on  a  fitting 
which  protects  the  'wires  and  lamps  from  the  weather.  The  circuit  wires 
are  installed  in  rigid  conduits  and  because  of  the  nature  of  the  fittings  used 
the  lamps  are  not  enclosed  in  sealed  globes. 


Courtesy  of  Hanlon  and   Murphy. 

Connecticut  River  Bridge  at  Hartford,  Conn. 

CAR  WIRING. 

In  the  rules  for  the  wiring  of  electric  cars,  and  the  equip- 
ment of  such  cars,  two  provisions  are  to  be  considered.  The 
protection  of  car  bodies  and  woodwork  over  all  of  the  electri- 
cal apparatus  such  as  motors,  resistance,  contactors,  heaters, 
and  the  like,  and  over  such  of  the  conductors  as  are  not  in- 
stalled in  conduit.  The  other  provides  for  wires,  cables,  and 
methods  of  making  joints  and  connections  in  them,  to  the 
location  and  type  of  fuse  and  circuit-breakers  to  be  used,  to 
special  forms  of  conduit  and  moulding,  and  to  details  of  the 
lighting,  heating,  and  air-pump  circuits.  As  all  of  these  re- 
quirements are  somewhat  outside  the  range  of  this  course,  I 
would  suggest  that  the  current  issue  of  the  National  Electrical 
Code  be  studied  in  detail. 

CAR  HOUSES  AND  SHOPS. 

Car  houses  and  car  repair  shops  have  electrical  hazards 
which  can  be  greatly  minimized  by  close  adherence  to  the 
special  rules  which  are  determined  chiefly  by  the  fact  that  the 
railway  circuit  is  grounded  and  this  requires  different  treat- 
ment than  the  ordinary  light  and  power  circuits.  The  trolley 
wires  must  be  securely  supported  on  insulating  hangers,  the 
hangers  to  be  so  spaced  that  should  a  trolley  wire  break,  con- 
tact with  the  floor  cannot  be  made.  There  should  be  an 
emergency  switch  outside  of  the  building,  that  all  the  trolley 
wires  in  the  building  may  be  cut  out  at  one  point,  and  the 


no 

trolley  wire  be  dead  at  all  points  within  100  feet  of  the  build- 
ing. It  is  also  desired  that  the  lighting  and  power  systems  be 
so  installed  that  one  main  switch  may  control  the  installation 
independently  of  the  main  cut-out  switch  outside  of  the  build- 
ing. That  the  amount  of  current  may  be  limited,  it  is  de- 
sirable that  the  installation  be  fed  through  an  automatic 
circuit-breaker.  It  is  now  the  practice  to  install  the  wires  of 
the  lighting  and  power  circuits  in  a  car  house  or  a  car  repair 
shop  in  metal  Conduits. 

LIGHTING  AND  POWER 
FROM  RAILWAY  WIRES. 

It  should  be  remembered  that  the  trolley  wires  of  a  rail- 
way system  have  a  grounded  return  and  that  the  wires  are 
exposed  to  lightning.  For  this  reason,  in  other  than  railway 
properties,  it  must  be  noted  that  under  no  circumstances 
should  current  for  electric  lighting  or  power  be  taken  from 
trolley  or  third-rail  railway  circuits  with  a  grounded  return. 
The  inevitable  fluctuation  in  voltage  would  frequently  require 
overfusing  of  the  circuits  to  prevent  blowing  of  fuses  under 
normal  conditions.  Then  a  circuit,  grounded  to  earth,  with 
so  much  capacity  behind  it  should  be  kept  out  of  factories  and 
buildings  of  all  kinds,  Except,  as  noted,  in  railway  properties. 

GARAGES. 

In  garages,  in  which  vehicles  carrying  volatile  inflam- 
mable liquid  for  fuel  or  power  are  kept,  for  whatever  purpose, 
we  have  a  hazard  which  is  not  directly  of  an  electrical  nature 
but  which  may  be  greatly  increased  through  an  imperfect 
electrical  installation.  All  feed  and  circuit  wires  should  be 
installed  in  conduit  or  armored  cables  and  all  outlet,  switch 
and  junction  boxes  should  be  located  at  least  4  feet  from  the 
floor.  All  cut-outs,  switches,  receptacles  and  any  device  hav- 
ing a  current  breaking  part  must  be  placed  at  least  4  feet  from 
the  floor,  that  the  vapor  from  gasoline,  due  to  leaks,  cannot 
be  ignited  by  the  arc  caused  by  breaking  the  circuit.  All 
portable  lights  must  have  keyless  sockets  of  moulded  compo- 
sition or  metal  sheathed  porcelain  type,  which  sockets  must 
,be  equipped  with  handle,  hook  and  substantial  guard.  Motors 
and  dynamos,  not  a  part  of  a  vehicle,  if  not  located  at  least  4 
feet  from  the  floor  must  be  of  the  fully  enclosed  type. 


Ill 

ELECTRIC  CRANES. 

The  chief  hazard  of  electric  cranes  is  to  be  found  in  the 
collector  wires,  which  wires  must  necessarily  be  bare.  These 
wires  must  be  so  mounted  on  insulating  supports,  that  even 
with  extreme  movements  the  wires  will  be  separated  at  all 
times  at  least  ~Ll/2  inches  from  the  surface  wired  over.  In  the 
horizontal  runs  of  the  collector  wires,  they  should  be  so 
supported  that  the  wires  will  be  at  least  6  inches  apart.  Owing 
to  the  intermittent  load  on  the  motors  the  resistances  are 
heated  considerably,  requiring  location  for  ample  ventilation. 
The  motor  frames,  and  the  entire  frame  of  the  crane  and  the 
tracks  must  be  permanently  and  effectually  grounded. 

LIST  OF  APPROVED  FITTINGS. 

You  will  recall  that  during  our  first  lecture  reference  was 
made  to  the  list  of  Approved  Fittings.  No  care  in  installing 
electrical  equipments  will  entirely  compensate  for  the  use  of 
inferior  or  defective  devices.  The  National  Board  of  Fire 
Underwriters  has  for  many  years  maintained  a  system  of 
tests  and  examinations  of  electrical  appliances,  and  issues 
twice  a  year  a  "List  of  Electrical  Appliances"  which  contains 
a  classified  form  under  the  names  of  their  manufacturers  all 
of  the  standard  and  special  fittings  and  materials  which  have 
been  approved. 

These  tests  and  examinations  are  made  and  the  approvals 
are  issued  by  the  Underwriters'  Laboratories.  The  con- 
structional details  of  electrical  fittings  and  materials  together 
with  the  chief  tests  to  which  they  are  subjected,  prior  to 
approval,  are  contained  in  what  is  known  as  Class  "D",  of  the 
National  Electrical  Code,  to  which  82  pages  are  devoted  to 
the  specifications  of  electrical  fittings  and  materials,  that,  in 
so  far  as  the  manufacturers  are  concerned,  electrical  installa- 
tions may  be  free  from  fire  hazards. 

SIGNALING  SYSTEMS. 

The  rules  for  signaling  systems  govern  wiring  for  tele- 
phone, telegraph,  (except  wireless  telegraph  apparatus) 
district  messenger,  call  bell  circuits,  fire  and  burglar  alarms 
and  similar  systems  which  are  dangerous  and  hazardous  only 
because  of  their  liability  to  become  crossed  with  electric  light, 
heat  or  power  circuits,  or  from  lightning.  When  on  pole  lines 


112 

with  wires  for  electric  light  and  power,  the  signaling  wires, 
being  smaller  and  more  liable  to  break  and  fall,  should  gener- 
ally be  placed  on  the  lower  cross-arms.  When  run  under- 
ground, they  should  never  be  in  the  same  duct  or  man-hole 
with  electric  light  or  power  wires,  owing  to  the  possibility  of 
the  two  systems  becoming  crossed.  When  these  systems 
enter  a  building  from  an  overhead  pole  line,  they  should  be 
provided  with  proper  protection  at  the  point  where  the  wires 
enter  the  building,  there  being  a  secondary  hazard  to  these 
signaling  systems,  owing  to  the  fact  that  in  the  extent  and 
ramification  of  all  electrical  wires  there  are  liabilities  of  mis- 
hap when,  through  accident,  there  is  contact  of  the  wires  of 
different  systems,  and  lighting  or  power  currents  are  imposed 
upon  the  delicate  apparatus  of  the  telephone  system ;  and  this 
hazard  is  set  aside  by  the  operation  of  protectors. 

PROTECTORS  TO  SIGNALING  SYSTEMS. 

At  the  ends  of  the  telephone  lines  destructive  results  from 
such  foreign  currents  are  prevented  by  apparatus  which  is 
sub-divided  into  the  various  functions  which  it  performs,  for 
there  has  not  been  thus  far  any  single  device  of  defending  the 
telephone  instruments  against  the  whole  range  of  commercial 
foreign  currents  and  lightning  to  which  they  are  subjected. 

The  first  element  consists  of  a  fuse  made  of  an  alloy  which 
forms  part  of  the  circuit,  and  is  contained  in  a  tube  of  vulcan- 
ized fiber.  These  fuses  wrill  deflagrate  when  exposed  to  cur- 
rents of  7  to  10  amperes,  the  capacity  of  the  fuse  varies 
according  to  the  type  of  apparatus. 


Courtesy   of   The   Insurance   Field. 


Standard  protector  used  by  the  American  Telephone  and  Telegraph 
Co.  a-a  are  the  enclosed  fuses,  b-b,  heat  coils.  If  a  grounded  current 
of  a  pressure  greater  than  300  volts  enters  the  building,  it  will  jump  the 
air  space  between  the  lightning  arrester  C  to  the  ground  plate  D. 


The  next  element  consists  of  a  pair  of  small  blocks  of 
carbon  whose  larger  surface  measures  about  one-half  inch, 
and  one  of  these  blocks  is  connected  to  the  telephone  circuit. 
The  corresponding  block  of  the  pair  of  carbons  is  separated 
from  it  by  a  perforated  sheet  of  iron  and  is  electrically  con- 
nected with  the  earth.  A  small  cavity  in  one  of  the  opposite 
faces  of  the  carbon  is  filled  with  a  button  of  solder  such  as 
used  in  automatic  sprinklers,  and  which  melts  at  160  degrees 
Fahr.  The  distance  between  these  carbons  or  the  thickness 
of  the  mica,  is  .0055  inch,  being  such  that  electricity  at  over 
350  volts  will  pass  from  the  carbon  connected  with  the  tele- 
phone circuit  across  this  space  to  the  opposite  carbon  and 
thence  to  the  earth,  thereby  relieving  the  telephonic  apparatus 
of  electrical  tension  exceeding  350  volts. 


Courtesy   of   The   Insurance    Field. 


At  "a"  in  _  the  above  picture  is  shown  a  heat  coil  mounted  between 
the  line  and  instrument  terminals  b  &  c,  the  spring  c  being  thereby 
held  at  a  tension.  As  soon  as  the  fused  metal  in  the  coil  melts,  spring  c 
is  released  and  flies  back,  opening  the  line  to  the  instrument  and  coming 
into  contact  with  ground  connection  d,  lets  the  current  from  the  outside 
line  be  carried  straight  to  earth  over  the  ground  wire.  If  this  is  a  heavy 
current  it  will  blow  the  fuses  which  have  been  placed  in  the  line  ahead 
and  cut  the  wires  out  of  circuit.  The  lightning  arresters  are  shown  at  f. 

Thus,  if  the  foreign  current  exceeds  the  carrying  capacity 
of  the  tubular  fuse,  its  deflagration  opens  the  circuit  at  that 
point.  If,  however,  it  is  less  in  volume  than  the  carrying 
capacity  of  the  fuse,  and  over  350  volts  tension,  it  leaps  across 
the  thin  space  separating  the  carbons,  and  thence  passes  to 
earth.  The  resistance  of  the  small  arc  in  the  space  between 
the  carbons  is  sufficient  to  slightly  warm  the  carbons,  and 
cause  the  fusible  metal  to  flow  from  its  recess  and  fill  the  space 
between  the  carbons,  and  thus  establishes  a  conductor  of  low 
resistance  to  earth.  This  diminished  resistance  generally 
causes  a  sufficient  increase  in  the  current  imposed  upon  a  line 
to  cause  the  tubular  fuse  to  deflagrate  and  open  the  circuit, 


H4 

if  it  did  not  do  so  on  the  first  occurrence  of  the  contact  which 
imposed  the  foreign  current  on.  the  telephone  circuit. 


Courtesy  of  The  Insurance  Field. 

A  type  of  protector  used  where  heat  coils  are  unnecessary. 

In  order  to  protect  the  fine  wires  of  the  telephonic  ap- 
paratus from  injury  by  currents  which  are  too  small  to  operate 
the  tubular  fuse,  and  of  too  low  tension  to  pass  to  earth 
through  the  carbon  cutouts,  a  third  element  known  as  the 
heat  coil  is  employed,  in  which  a  fine  German  silver  w7ire 
which  forms  a  part  of  the  telephone  circuit  will  be  heated  by  a 
current  on  %  ampere  to  a  temperature  sufficient  to  release  a 
conductor  ordinarily  secured  by  fusible  solder,  and  pass  the 
current  to  earth.  The  result  of  this  protective  apparatus  is 
to  guard  against  mishaps  to  the  apparatus  resulting  from 
foreign  currents  and  lightning. 

WIRELESS  TELEGRAPH  APPARATUS. 

Another  form  of  signaling  system  has  come  into  popular 
use  in  the  form  of  wireless  telegraphy.  This  consists  of  a 
number  of  bare  wires  supported  through  insulators  on  wooden 
spreaders,  which  spreaders  are  supported  overhead,  generally, 
from  wooden  masts,  and  because  of  the  exposure  to  the 
elements,  are  liable  to  high  potential  surges  from  high-poten- 
tial transmission  lines  within  the  range  of  the  apparatus  and 
from  lightning.  When  these  equipments  are  not  in  use,  they 
should  be  effectively  connected  to  earth  that  the  surges  and 
lightning  discharges  may  have  an  easy  path  to  ground. 

MARINE  INSTALLATIONS. 

These  installations  are  on  vessels  and  must  be  well  pro- 
tected against  moisture,  since  the  salt  air  and  fogs  destroy 
ordinary  fittings  and  materials.  The  rules  for  this  type  of 
installation  differs  from  the  standard  rules  in  that  special  care 
is  necessary  to  guard  against  the  effects  of  constant  and 


Aenol 


To  Receiving  Set 


lOOMmpere 
^  Knife 
Switch 


No.4  8*5 
Gouge  Copper 
Wire 


Ground  or 

Water 
'Pipe, 
Street  Side. 


To  Sending  Set 


Grounding  aerial  by  knife  switch  on  outside  of  building. 

severe  vibration,  dampness  and  extreme  hard  usage  to  which 
installations  of  vessels  are  always  subjected.  Wires  arc- 
usually  installed  in  conduit  or  in  moulding.  Lead  encased 
cables  have  been  used  in  the  wiring  of  battleships,  but  such 
method  of  installation  has  not  been  a  success  owing  to  the 
cracking  of  the  protective  lead  covering  which  permitted 
moisture  to  enter  and  in  a  short  time  the  rubber  insulation 
was  destroyed. 


ELECTRICAL   FIRE    HAZARDS 
(A  Review.) 

In  electric  power  installations,  attention  should  be  given 

to  the  following  features : — 

Switchboards  of  wood  or  wood-skeleton  type,  treated  with 
oil,  varnish  or  insulating  compound,  are  of  antiquated 
type,  and  should  be  replaced  by  those  of  modern  design, 
constructed  entirely  of  non-combustible,  non-absorptive, 
insulating  materials.  Switchboards  built  of  planks  closely 
nailed  together  are  especially  dangerous. 

All  switchboards  must  be  provided  with  a  reliable  ground- 
detecting  device  and  necessary  circuit  breakers  or  fuses  of 
a  standard  type. 

Observe  that  terminals  of  underground  conduit  or  ducts  at 
both  generator  and  switchboard  are  properly  sealed  and 
so  located  as  to  prevent  the  entrance  of  water  or  dirt 
therein.  All  such  terminals  should  extend  above  floor 
line  the  full  limit  of  available  space. 


(d)  Fuses  require  constant  supervision  and  should  be  preferably 

of  the  enclosed  type. 

(e)  Space  behind  switchboard  must  be  kept  free  from  rubbish  or 

combustible  materials. 

(f)  All  outgoing  lines  should  be  provided  with  approved  lightning 

arresters. 

(g)  The  arrangement  and  spacing  of  cables  should  be  observed. 

Even  in  instances  of  lead  covered  cables  an  arc  may  melt 
off  the  lead  and  burn  the  insulation.  Cables  should  not 
be  too  closely  bunched  or  grouped;  extensive  damage  to 
insulation  may  result  from  fire  in  bunched  cables. 

(h)  Old-fashioned  oil  switches  with  open  top  and  wrooden  interi- 
ors, where  found,  should  be  replaced  with  approved  de- 
vices. 

(i)  Current  transmitted  from  high-voltage  lines  should  enter 
transformers  properly  installed  outside  of  buildings,  or  in 
a  well  ventilated  fireproof  vault  properly  cut-off.  Oil- 
filled  transformers  should  always  be  surrounded  by  a 
curbing  of  sufficient  height  to  contain  as  much  oil  as  is 
contained  in  the  transformers  themselves,  and  ample 
drainage  should  be  provided  at  floor  level.  Note  that  oil- 
filled  transformers  should  never  be  installed  inside  of  main 
building,  if  possible  to  avoid  it. 

(j)  No  oils  or  volatiles  of  any  kind  should  be  kept  in  generator 
room  except  the  daily  supply  of  lubricating  oils  in  metal 
receptacles.  There  should  be  no  accumulations  of  dry  or 
used  waste  in  generator  room.  Adequate  standard  metal 
waste  cans  and  hand  fire  protection  should  be  installed. 


ELECTRIC  MOTORS. 

All  motors  should  be  installed  in  a  dry  and  well  lighted 
location,  to  which  free  access  may  be  had  at  all  times. 

(a)  Motors  should  be  equipped  with  a  substantial  metal  drip  pan 

to  catch  all  waste  oil. 

(b)  All  motors,  regardless  of  size,  should  be  protected  by  proper 

fuses  or  circuit  breakers,  and  switches  at  each  motor 
should  be  of  a  type  that  will  positively  cut-off  all  current 
when  motor  is  not  in  operation.  All  starting  boxes  and 
controlling  devices,  except  in  specially  authorized  cases, 
should  be  in  immediate  sight  of  motor. 

(c)  All  motors  installed  in  dusty  and  dirty  places  where  readily 

ignitable  material  is  present,  should  be  of  enclosed  type  or 
be  placed  in  enclosures  constructed  preferably  of  non- 
combustible  material  with  ample  amount  of  fine  wire 
screen  to  afford  good  ventilation. 

(d)  To  avoid  such  locations  where  possible,  it  is  advisable  that 

motor  should  drive  machinery  through  the  medium  of  a 
shaft  fitting  tightly  in  a  wall  bushing,  motor  being  on 
opposite  side  of  wall  or  partition. 


(e)  All 'rheostats  and  starting  boxes,  unless  mounted  on  switch- 

boards, should  be  mounted  on  slate  or  other  non-com- 
bustible insulating  material,  unless  mounted  on  substan- 
tial brackets  which  will  separate  them  one  foot  from  com- 
bustible material,  or  unless  mounted  on  cement  or  con- 
crete walls  or  floors. 

(f)  Motors  must  be  of  sufficient  capacity;   must  be  kept  clean, 

must  be  regularly  oiled  and  otherwise  given  proper  care, 
and  commutators  kept  smooth. 

(g)  Motors  should  be  in   care  of  a  competent  man   who   should 

periodically  inspect  them. 

ELECTRIC  LIGHTING  HAZARDS. 

All  equipments  for  electric  lighting,  heating,  etc.  should 
conform  to  the  following,  which  are  suggestions  for  field 
practice. 

(a)  All  wires  must  be  properly  supported,  insulated  and  protected 

against  mechanical  injury,  so  that  system  may  be  kept 
/  free  from  grounds  and  short  circuits.  Observe  whether 
ground  wires  for  conduit  and  secondary  systems  remain 
undisturbed  and  that  connections  of  ground  wires  to 
conduit  and  water  pipe  or  other  grounded  metal  work  are 
also  undisturbed  and  in  good  order.  Telephone,  bell,  and 
other  signal  wires  should  also  be  observed  and  be  made 
free  from  contact  with  electric  light  wires.  Crosses  out- 
side are  frequently  as  dangerous  as  inside  of  buildings. 
Recommend  that  wires  be  made  rigid  and  free  from 
sagging. 

(b)  Wires  must  be  of  ample  capacity  to  prevent  overheating;  all 

joints  must  be  properly  soldered  and  taped  so  as  to  insure 
perfect  contact ;  wires  must  be  protected  by  fuses  of  proper 
size  and  of  approved  type  against  overload  and  short 
circuits. 

(c)  If  installed  in  the  vicinity  of  easily  ignitable  material,   cut- 

outs must  be  enclosed  in  standard  cabinets.  If  not  of 
metal,  cabinets  must  be  properly  lined.  Door,  latch,  and 
hinges  should  be  kept  in  proper  order.  Cut-outs  and 
switches  must  not  be  installed  in  rooms  subjected  to  in- 
flammable vapors,  nor  in  rooms  wherein  hazardous  pro- 
cesses are  conducted,  unless  by  special  permission  and 
provision  for  special  safeguards. 

(d)  Where  volatile  vapors  or  dangerous  explosives  are  prevalent, 

suggest  conduit  system  of  wiring  and  the  use  of  vapor- 
proof  globes.  Switches  and  cut-outs  controlling  these 
circuits  should  be  installed  outside  of  the  room  where  any 
hazardous  process  is  conducted,  unless  by  special  per- 
mission and  provision  for  special  safeguards.  Where 
necessary,  suggest  the  use  of  metal  guards  about  swinging 
globes. 


n8 

(e)  See  that  all  fuses  are  of  standard  type  and  in  good  condition. 

Suggest  the  removal  of  substitutes,  such  as  nails,  hairpins, 
and  the  like.  Observe  contact  parts  of  cartridge  fuse 
blocks. 

(f)  Observe  if  all  fixtures  are  properly  connected  and  supported; 

ascertain  if  any  circuits  are  overloaded  by  attachment  of 
too  many  lamps. 

(g)  All  pendant  lamps  must  be  provided  with  approved  cord,  and 

be  free  from  contact  with  furniture,  nails,  pipes,  machinery, 
and  other  fixtures.  Lamps  of  a  portable  type  must  be 
equipped  with  approved  reinforced  cord,  to  insure  pro- 
tection against  abrasion.  Heavy  guards  are  recommended 
for  lamps  attached  to  portable  cords. 

(h)  Condemn  the  use  of  paper  and  other  combustible  shades  on 
lamps.  Where  shades  are  necessary,  suggest  those  of  a 
non-combustible  type.  Recommend  the  removal  of  any 
temporary  attachments,  artistic  displays,  and  extensions 
improperly  made. 

(i)  Electric  heating  devices  should  be  protected  against  danger 
of  communicating  fire  to  adjacent  materials,  as  to  con- 
struction, connection  and  mounting.  Note  the  installation 
of  special  apparatus  such  as  electric  welding  machines, 
electric  furnaces  and  ovens,  cloth  cutters,  etc.,  etc.,  and  if 
such  apparatus  appears  carelessly  or  improperly  installed, 
notify  or  confer  with  the  inspection  department  having 
jurisdiction. 

(j)  Lighting  and  power  from  railway  wires  must  not  be  permitted 
under  any  pretense  on  the  same  circuit  with  trolley  wires 
with  a  ground  return,  except  in  railway  cars,  electric  car 
houses,  power  houses,  passenger  and  freight  stations  con- 
nected with  the  operation  of  electric  railways. 

(k)  Obsolete  types  of  electrical  equipments  are  occasionally  met 
with,  especially  hazardous  features  of  which  are  wooden 
cleats,  rosettes,  and  fuse  blocks,  knife  switches  of  unsafe 
dimensions,  often  mounted  upon  wooden  bases  and 
wooden  case  rheostats.  Wires  and  flexible  cord  in  such 
instances  will  be  found  to  have  very  inferior  insulation. 
Equipments  of  this  character  should  usually  be  replaced, 
as  in  most  cases  they  may  be  considered  as  beyond  possi- 
ble repair  short  of  a  new  installation. 

Bibliography. 

Associated  Factory  Mutual  Fire  Insurance  Companies:  Rules 
for  electric  light  and  power  equipments,  consisting  of  the 
National  Electrical  Code,  with  supplementary  notes.  Ed. 
of  1915.  Inspection  Department,  31  Milk  Street,  Boston. 

Ralph  Sweetland  :  Electrical  Hazards.  Four  lectures  delivered 
before  the  Insurance  Institute,  Boston,  Mass.,  1911.  The 
Insurance  Library  Association,  141  Milk  Street,  Boston, 
Mass. 


Tig 

Washington  Devcrcux:  Electrical  Key,  for  use  of  electrical 
inspection  bureaus  in  advising  electrical  contractors, 
wiremen,  etc.,  of  corrections  required  so  that  installations 
will  conform  to  the  National  Electrical  Code.  Published 
by  the  author,  Phila.,  Pa. 

Horstman  &  Tousley:  Modern  Electrical  Construction.  2nd 
Edition.  Frederick  J.  Drake  &  Co.,  Chicago,  1908. 

National  Board  of  Fire  Underwriters:  Rules  and  Require- 
ments for  electric  wiring  and  apparatus  as  recommended 
by  the  National  Fire  Protection  Assoc.  Edition  of  1915, 
with  changes  suggested  for  the  1918  edition.  Boston, 
Mass. 

Dana  Pierce :  Underwriters'  requirements  for  safe  electrical 
installations.  Volume  3,  Cyclopedia  of  Fire  Prevention 
and  Insurance. 

A.  M.  Schoen :  Manual  of  electricity.  A  reference  book  for 
the  use  of  fire  underwriters.  Louisville,  Ky.,  1911.  The 
Insurance  Field  Co. 

C.  J.  H.  Woodbury:  The  Electrical  Fire  Hazard.  Boston, 
Mass.  1905.  Alfred  Mudge  &  Son. 

C.  J.  H.  Woodbury :  History  of  the  National  Electrical  Code. 
1906.  National  Electrical  Contractor.  Utica,  N.  Y. 

Terrell  Croft:  American  Electricians'  Hand  Book.  A  refer- 
ence '  book  for  practical  electrical  workers.  1914. 
McGraw-Hill  Book  Co. 

W.  H.  Timbie:  Essentials  of  Electricity.  1914.  John  Wiley 
&  Sons. 

W.  H.  Timbie :  Elements  of  Electricity.  1914.  John  Wiley  & 
Sons,  N.  Y. 

C.  E.  Knox:  Electric  Light  Wiring!  1907.  McGraw  Pub.  Co., 
N.  Y. 

W.  E.  Barrows:  Electrical  Illuminating  Engineer.  1908. 
McGraw  Pub.  Co. 

Newton  Harrison:  Electric-Wiring,  Diagrams  and  Switch- 
boards. 1906.  The  Norman  W.  Hanley  Publishing  Com- 
pany, N.  Y. 

Albert  Blauvelt:  Electrical  Fire  Hazard:  How  to  judge  it 
and  what  to  do.  1895.  Rollins  Publishing  Co.,  Chicago. 

Edwin  J.  Houston :  Electricity,  One  Hundred  Years  Ago  and 
To-day.  1894.  McGraw  Pub.  Co. 

Nicholas  Power: — "Power's  Cameragraph."    1910.   Catalogue, 

Nicholas  Power  Co.,  N.  Y. 

A.  E.  Watson :  A  Handbook  of  Wiring  Tables.  1904.  Bubier 
Pub.  Co.  Lynn,  Mass. 

American  Institute  of  Electrical  Engineers:  Standardization 
Rules.  1915-  New  York. 

W.  J.  Canada:  The  Hazards  of  Domestic  Electrical  Appli- 
ances. Quarterly  National  Fire  Protection  Assoc.,  Octo- 
ber, 1917- 


I2O 

Chester  H.  Thordardson :  The  Toy  Transformer  and  its 
Hazards.  Quarterly  National  Fire  Protection  Assoc. 
October,  1917. 

Underwriters  Laboratories:  Electrical  Data,  March,  1916. 
February  and  July,  1917,  Chicago. 

National  Board  of  Fire  Underwriters:  Storage  and  Handling 
of  Nitrocellulose  Motion  Picture  Films,  as  recommended 
by  the  National  Fire  Protection  Assoc.,  1915,  Boston. 

F.  A.  Talbot :  Moving  Pictures :  How  they  are  made  and 
worked.  1912.  J.  B.  Lippincott  Co.,  Phila. 


DEPT. 

«! 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


